<!DOCTYPE html>
<html>
<body>
<h1>My first PHP page</h1>
<?php
echo "Hello World!";
?>
</body>
</html>
----------------------------
<!DOCTYPE html>
<html>
<body>
<?php
// This is a single line comment
# This is also a single line comment
/*
This is a multiple lines comment block
that spans over more than
one line
*/
?>
</body>
</html>
---------------------------------------
In the example below, all three echo statements below are legal (and equal):
<html>
<body>
<h1>My first PHP page</h1>
<?php
echo "Hello World!";
?>
</body>
</html>
----------------------------
<!DOCTYPE html>
<html>
<body>
<?php
// This is a single line comment
# This is also a single line comment
/*
This is a multiple lines comment block
that spans over more than
one line
*/
?>
</body>
</html>
---------------------------------------
PHP Case Sensitivity
In PHP, all user-defined functions, classes, and keywords (e.g. if, else, while, echo, etc.) are case-insensitive.In the example below, all three echo statements below are legal (and equal):
Example
<!DOCTYPE html>
<html>
<body>
<?php
ECHO "Hello World!<br>";
echo "Hello World!<br>";
EcHo "Hello World!<br>";
?>
</body>
</html>
<html>
<body>
<?php
ECHO "Hello World!<br>";
echo "Hello World!<br>";
EcHo "Hello World!<br>";
?>
</body>
</html>
-------------------------------------
However; in PHP, all variables are case-sensitive.
In the example below, only the first statement will display the value of the $color variable (this is because $color, $COLOR, and $coLOR are treated as three different variables):
A variable is created the moment you first assign a value to it:
A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function.
The following example tests variables with local and global scope:
To do this, use the global keyword before the variables (inside the function):
Display Strings
The following example shows how to display different strings with the echo command (also notice that the strings can contain HTML markup):
Display Variables
The following example shows how to display strings and variables with the echo command:
Display Strings
The following example shows how to display different strings with the print command (also notice that the strings can contain HTML markup):
Display Variables
The following example shows how to display strings and variables with the print command:
A string can be any text inside quotes. You can use single or double quotes:
Rules for integers:
In the following example we will test different numbers. The PHP var_dump() function returns the data type and value of variables:
Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial.
In the following example we create an array, and then use the PHP var_dump() function to return the data type and value of the array:
In PHP, an object must be explicitly declared.
First we must declare a class of object. For this, we use the class keyword. A class is a structure that can contain properties and methods.
We then define the data type in the object class, and then we use the data type in instances of that class:
The NULL value identifies whether a variable is empty or not. Also useful to differentiate between the empty string and null values of databases.
Variables can be emptied by setting the value to NULL:
The example below returns the length of the string "Hello world!":
If a match is found, it will return the character position of the first match. If no match is found, it will return FALSE.
The example below searches for the text "world" in the string "Hello world!":
The output of the code above will be: 6.
-------------------------------
A valid constant name starts with a letter or underscore (no $ sign before the constant name).
Note: Unlike valriables, constants are automatically global across the entire script.
The example below creates a case-sensitive constant, with the value of "Welcome to W3Schools.com!":
The example below shows the different results of using the different arithmetic operators:
The basic assignment operator in PHP is "=". It means that the left operand gets set to the value of the assignment expression on the right.
The example below shows the different results of using the different assignment operators:
The example below shows the results of using the string operators:
The example below shows the different results of using the different increment/decrement operators:
The example below shows the different results of using some of the comparison operators:
The example below shows the different results of using the different array operators:
In PHP we have the following conditional statements:
The example below will output "Have a good day!" if the current time (HOUR) is less than 20:
The example below will output "Have a good day!" if the current time is less than 20, and "Have a good night!" otherwise:
The example below will output "Have a good morning!" if the current time is less than 10, and "Have a good day!" if the current time is less than 20. Otherwise it will output "Have a good night!":
Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.
Note: However, there is an 8 MB max size for the POST method, by default (can be changed by setting the post_max_size in the php.ini file).
When the user clicks the "Submit" button, the URL will look like this:
The "welcome.php" file can now use the $_POST variable to collect form data (the names of the form fields will automatically be the keys in the $_POST array):
However, because the variables are not displayed in the URL, it is not possible to bookmark the page.
The $_REQUEST variable can be used to collect form data sent with both the GET and POST methods.
In the example below, only the first statement will display the value of the $color variable (this is because $color, $COLOR, and $coLOR are treated as three different variables):
Example
<!DOCTYPE html>
<html>
<body>
<?php
$color="red";
echo "My car is " . $color . "<br>";
echo "My house is " . $COLOR . "<br>";
echo "My boat is " . $coLOR . "<br>";
?>
</body>
</html>
<html>
<body>
<?php
$color="red";
echo "My car is " . $color . "<br>";
echo "My house is " . $COLOR . "<br>";
echo "My boat is " . $coLOR . "<br>";
?>
</body>
</html>
-------------------------
Variables are "containers" for storing information:
Example
<?php
$x=5;
$y=6;
$z=$x+$y;
echo $z;
?>
$x=5;
$y=6;
$z=$x+$y;
echo $z;
?>
-------------
Creating (Declaring) PHP Variables
PHP has no command for declaring a variable.A variable is created the moment you first assign a value to it:
Example
<?php
$txt="Hello world!";
$x=5;
$y=10.5;
?>
$txt="Hello world!";
$x=5;
$y=10.5;
?>
-----------------------------------
Local and Global Scope
A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function.A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function.
The following example tests variables with local and global scope:
Example
<?php
$x=5; // global scope
function myTest()
{
$y=10; // local scope
echo "<p>Test variables inside the function:<p>";
echo "Variable x is: $x";
echo "<br>";
echo "Variable y is: $y";
}
myTest();
echo "<p>Test variables outside the function:<p>";
echo "Variable x is: $x";
echo "<br>";
echo "Variable y is: $y";
?>
$x=5; // global scope
function myTest()
{
$y=10; // local scope
echo "<p>Test variables inside the function:<p>";
echo "Variable x is: $x";
echo "<br>";
echo "Variable y is: $y";
}
myTest();
echo "<p>Test variables outside the function:<p>";
echo "Variable x is: $x";
echo "<br>";
echo "Variable y is: $y";
?>
---------------------------------------
PHP The global Keyword
The global keyword is used to access a global variable from within a function.To do this, use the global keyword before the variables (inside the function):
Example
<?php
$x=5;
$y=10;
function myTest()
{
global $x,$y;
$y=$x+$y;
}
myTest();
echo $y; // outputs 15
?>
$x=5;
$y=10;
function myTest()
{
global $x,$y;
$y=$x+$y;
}
myTest();
echo $y; // outputs 15
?>
PHP also stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable. This array is also accessible from within functions and can be used to update global variables directly.
The example above can be rewritten like this:
To do this, use the static keyword when you first declare the variable:
Then, each time the function is called, that variable will still have the information it contained from the last time the function was called.
Note: The variable is still local to the function.
The example above can be rewritten like this:
Example
<?php
$x=5;
$y=10;
function myTest()
{
$GLOBALS['y']=$GLOBALS['x']+$GLOBALS['y'];
}
myTest();
echo $y; // outputs 15
?>
$x=5;
$y=10;
function myTest()
{
$GLOBALS['y']=$GLOBALS['x']+$GLOBALS['y'];
}
myTest();
echo $y; // outputs 15
?>
PHP The static Keyword
Normally, when a function is completed/executed, all of its variables are deleted. However, sometimes we want a local variable NOT to be deleted. We need it for a further job.To do this, use the static keyword when you first declare the variable:
Example
<?php
function myTest()
{
static $x=0;
echo $x;
$x++;
}
myTest();
myTest();
myTest();
?>
function myTest()
{
static $x=0;
echo $x;
$x++;
}
myTest();
myTest();
myTest();
?>
Note: The variable is still local to the function.
----------------------------
In PHP there is two basic ways to get output: echo and print.
In this tutorial we use echo (and print) in almost every example. So, this chapter contains a little more info about those two output statements.
PHP echo and print Statements
There are some difference between echo and print:- echo - can output one or more strings
- print - can only output one string, and returns always 1
The PHP echo Statement
echo is a language construct, and can be used with or without parantheses: echo or echo().Display Strings
The following example shows how to display different strings with the echo command (also notice that the strings can contain HTML markup):
Example
<?php
echo "<h2>PHP is fun!</h2>";
echo "Hello world!<br>";
echo "I'm about to learn PHP!<br>";
echo "This", " string", " was", " made", " with multiple parameters.";
?>
echo "<h2>PHP is fun!</h2>";
echo "Hello world!<br>";
echo "I'm about to learn PHP!<br>";
echo "This", " string", " was", " made", " with multiple parameters.";
?>
The following example shows how to display strings and variables with the echo command:
Example
<?php
$txt1="Learn PHP";
$txt2="W3Schools.com";
$cars=array("Volvo","BMW","Toyota");
echo $txt1;
echo "<br>";
echo "Study PHP at $txt2";
echo "My car is a {$cars[0]}";
?>
$txt1="Learn PHP";
$txt2="W3Schools.com";
$cars=array("Volvo","BMW","Toyota");
echo $txt1;
echo "<br>";
echo "Study PHP at $txt2";
echo "My car is a {$cars[0]}";
?>
The PHP print Statement
print is also a language construct, and can be used with or without parantheses: print or print().Display Strings
The following example shows how to display different strings with the print command (also notice that the strings can contain HTML markup):
Example
<?php
print "<h2>PHP is fun!</h2>";
print "Hello world!<br>";
print "I'm about to learn PHP!";
?>
print "<h2>PHP is fun!</h2>";
print "Hello world!<br>";
print "I'm about to learn PHP!";
?>
The following example shows how to display strings and variables with the print command:
Example
<?php
$txt1="Learn PHP";
$txt2="W3Schools.com";
$cars=array("Volvo","BMW","Toyota");
print $txt1;
print "<br>";
print "Study PHP at $txt2";
print "My car is a {$cars[0]}";
?>
$txt1="Learn PHP";
$txt2="W3Schools.com";
$cars=array("Volvo","BMW","Toyota");
print $txt1;
print "<br>";
print "Study PHP at $txt2";
print "My car is a {$cars[0]}";
?>
----------------
PHP Strings
A string is a sequence of characters, like "Hello world!".A string can be any text inside quotes. You can use single or double quotes:
Example
<?php
$x = "Hello world!";
echo $x;
echo "<br>";
$x = 'Hello world!';
echo $x;
?>
$x = "Hello world!";
echo $x;
echo "<br>";
$x = 'Hello world!';
echo $x;
?>
PHP Integers
An integer is a number without decimals.Rules for integers:
- An integer must have at least one digit (0-9)
- An integer cannot contain comma or blanks
- An integer must not have a decimal point
- An integer can be either positive or negative
- Integers can be specified in three formats: decimal (10-based), hexadecimal (16-based - prefixed with 0x) or octal (8-based - prefixed with 0)
Example
<?php
$x = 5985;
var_dump($x);
echo "<br>";
$x = -345; // negative number
var_dump($x);
echo "<br>";
$x = 0x8C; // hexadecimal number
var_dump($x);
echo "<br>";
$x = 047; // octal number
var_dump($x);
?>
$x = 5985;
var_dump($x);
echo "<br>";
$x = -345; // negative number
var_dump($x);
echo "<br>";
$x = 0x8C; // hexadecimal number
var_dump($x);
echo "<br>";
$x = 047; // octal number
var_dump($x);
?>
PHP Floating Point Numbers
A floating point number is a number with a decimal point or a number in exponential form.In the following example we will test different numbers. The PHP var_dump() function returns the data type and value of variables:
Example
<?php
$x = 10.365;
var_dump($x);
echo "<br>";
$x = 2.4e3;
var_dump($x);
echo "<br>";
$x = 8E-5;
var_dump($x);
?>
$x = 10.365;
var_dump($x);
echo "<br>";
$x = 2.4e3;
var_dump($x);
echo "<br>";
$x = 8E-5;
var_dump($x);
?>
PHP Booleans
Booleans can be either TRUE or FALSE.var x=true;
var y=false;
var y=false;
PHP Arrays
An array stores multiple values in one single variable.In the following example we create an array, and then use the PHP var_dump() function to return the data type and value of the array:
Example
<?php
$cars=array("Volvo","BMW","Toyota");
var_dump($cars);
?>
$cars=array("Volvo","BMW","Toyota");
var_dump($cars);
?>
PHP Objects
An object is a data type which stores data and information on how to process that data.In PHP, an object must be explicitly declared.
First we must declare a class of object. For this, we use the class keyword. A class is a structure that can contain properties and methods.
We then define the data type in the object class, and then we use the data type in instances of that class:
Example
<?php
class Car
{
var $color;
function Car($color="green")
{
$this->color = $color;
}
function what_color()
{
return $this->color;
}
}
?>
class Car
{
var $color;
function Car($color="green")
{
$this->color = $color;
}
function what_color()
{
return $this->color;
}
}
?>
PHP NULL Value
The special NULL value represents that a variable has no value. NULL is the only possible value of data type NULL.The NULL value identifies whether a variable is empty or not. Also useful to differentiate between the empty string and null values of databases.
Variables can be emptied by setting the value to NULL:
Example
<?php
$x="Hello world!";
$x=null;
var_dump($x);
?>
$x="Hello world!";
$x=null;
var_dump($x);
?>
A string is a sequence of characters, like "Hello world!".
PHP String Functions
In this chapter we will look at some commonly used functions to manipulate strings.The PHP strlen() function
The strlen() function returns the length of a string, in characters.The example below returns the length of the string "Hello world!":
Example
<?php
echo strlen("Hello world!");
?>
echo strlen("Hello world!");
?>
The output of the code above will be: 12
The PHP strpos() function
The strpos() function is used to search for a specified character or text within a string.If a match is found, it will return the character position of the first match. If no match is found, it will return FALSE.
The example below searches for the text "world" in the string "Hello world!":
Example
<?php
echo strpos("Hello world!","world");
?>
echo strpos("Hello world!","world");
?>
-------------------------------
Constants are like variables except that once they are defined they cannot be changed or undefined.
PHP Constants
A constant is an identifier (name) for a simple value. The value cannot be changed during the script.A valid constant name starts with a letter or underscore (no $ sign before the constant name).
Note: Unlike valriables, constants are automatically global across the entire script.
Set a PHP Constant
To set a constant, use the define() function - it takes three parameters: The first parameter defines the name of the constant, the second parameter defines the value of the constant, and the optional third parameter specifies whether the constant name should be case-insensitive. By default, the constant name is not case-insensitive.The example below creates a case-sensitive constant, with the value of "Welcome to W3Schools.com!":
Example
<?php
define("GREETING", "Welcome to W3Schools.com!");
echo GREETING;
?>
define("GREETING", "Welcome to W3Schools.com!");
echo GREETING;
?>
The example below creates a case-insensitive constant, with the value of "Welcome to W3Schools.com!":
Example
<?php
define("GREETING", "Welcome to W3Schools.com!", true);
echo greeting;
?>
define("GREETING", "Welcome to W3Schools.com!", true);
echo greeting;
?>
----------------------------
This chapter shows the different operators that can be used in PHP scripts.
PHP Arithmetic Operators
| Operator | Name | Example | Result |
|---|---|---|---|
| + | Addition | $x + $y | Sum of $x and $y |
| - | Subtraction | $x - $y | Difference of $x and $y |
| * | Multiplication | $x * $y | Product of $x and $y |
| / | Division | $x / $y | Quotient of $x and $y |
| % | Modulus | $x % $y | Remainder of $x divided by $y |
Example
<?php
$x=10;
$y=6;
echo ($x + $y); // outputs 16
echo ($x - $y); // outputs 4
echo ($x * $y); // outputs 60
echo ($x / $y); // outputs 1.6666666666667
echo ($x % $y); // outputs 4
?>
$x=10;
$y=6;
echo ($x + $y); // outputs 16
echo ($x - $y); // outputs 4
echo ($x * $y); // outputs 60
echo ($x / $y); // outputs 1.6666666666667
echo ($x % $y); // outputs 4
?>
-----------------------
PHP Assignment Operators
The PHP assignment operators is used to write a value to a variable.The basic assignment operator in PHP is "=". It means that the left operand gets set to the value of the assignment expression on the right.
| Assignment | Same as... | Description |
|---|---|---|
| x = y | x = y | The left operand gets set to the value of the expression on the right |
| x += y | x = x + y | Addition |
| x -= y | x = x - y | Subtraction |
| x *= y | x = x * y | Multiplication |
| x /= y | x = x / y | Division |
| x %= y | x = x % y | Modulus |
Example
<?php
$x=10;
echo $x; // outputs 10
$y=20;
$y += 100;
echo $y; // outputs 120
$z=50;
$z -= 25;
echo $z; // outputs 25
$i=5;
$i *= 6;
echo $i; // outputs 30
$j=10;
$j /= 5;
echo $j; // outputs 2
$k=15;
$k %= 4;
echo $k; // outputs 3
?>
$x=10;
echo $x; // outputs 10
$y=20;
$y += 100;
echo $y; // outputs 120
$z=50;
$z -= 25;
echo $z; // outputs 25
$i=5;
$i *= 6;
echo $i; // outputs 30
$j=10;
$j /= 5;
echo $j; // outputs 2
$k=15;
$k %= 4;
echo $k; // outputs 3
?>
PHP String Operators
| Operator | Name | Example | Result |
|---|---|---|---|
| . | Concatenation | $txt1 = "Hello" $txt2 = $txt1 . " world!" | Now $txt2 contains "Hello world!" |
| .= | Concatenation assignment | $txt1 = "Hello" $txt1 .= " world!" | Now $txt1 contains "Hello world!" |
Example
<?php
$a = "Hello";
$b = $a . " world!";
echo $b; // outputs Hello world!
$x="Hello";
$x .= " world!";
echo $x; // outputs Hello world!
?>
$a = "Hello";
$b = $a . " world!";
echo $b; // outputs Hello world!
$x="Hello";
$x .= " world!";
echo $x; // outputs Hello world!
?>
PHP Increment / Decrement Operators
| Operator | Name | Description |
|---|---|---|
| ++$x | Pre-increment | Increments $x by one, then returns $x |
| $x++ | Post-increment | Returns $x, then increments $x by one |
| --$x | Pre-decrement | Decrements $x by one, then returns $x |
| $x-- | Post-decrement | Returns $x, then decrements $x by one |
Example
<?php
$x=10;
echo ++$x; // outputs 11
$y=10;
echo $y++; // outputs 10
$z=5;
echo --$z; // outputs 4
$i=5;
echo $i--; // outputs 5
?>
$x=10;
echo ++$x; // outputs 11
$y=10;
echo $y++; // outputs 10
$z=5;
echo --$z; // outputs 4
$i=5;
echo $i--; // outputs 5
?>
PHP Comparison Operators
The PHP comparison operators are used to compare two values (number or string):| Operator | Name | Example | Result |
|---|---|---|---|
| == | Equal | $x == $y | True if $x is equal to $y |
| === | Identical | $x === $y | True if $x is equal to $y, and they are of the same type |
| != | Not equal | $x != $y | True if $x is not equal to $y |
| <> | Not equal | $x <> $y | True if $x is not equal to $y |
| !== | Not identical | $x !== $y | True if $x is not equal to $y, or they are not of the same type |
| > | Greater than | $x > $y | True if $x is greater than $y |
| < | Less than | $x < $y | True if $x is less than $y |
| >= | Greater than or equal to | $x >= $y | True if $x is greater than or equal to $y |
| <= | Less than or equal to | $x <= $y | True if $x is less than or equal to $y |
Example
<?php
$x=100;
$y="100";
var_dump($x == $y);
echo "<br>";
var_dump($x === $y);
echo "<br>";
var_dump($x != $y);
echo "<br>";
var_dump($x !== $y);
echo "<br>";
$a=50;
$b=90;
var_dump($a > $b);
echo "<br>";
var_dump($a < $b);
?>
$x=100;
$y="100";
var_dump($x == $y);
echo "<br>";
var_dump($x === $y);
echo "<br>";
var_dump($x != $y);
echo "<br>";
var_dump($x !== $y);
echo "<br>";
$a=50;
$b=90;
var_dump($a > $b);
echo "<br>";
var_dump($a < $b);
?>
PHP Logical Operators
| Operator | Name | Example | Result |
|---|---|---|---|
| and | And | $x and $y | True if both $x and $y are true |
| or | Or | $x or $y | True if either $x or $y is true |
| xor | Xor | $x xor $y | True if either $x or $y is true, but not both |
| && | And | $x && $y | True if both $x and $y are true |
| || | Or | $x || $y | True if either $x or $y is true |
| ! | Not | !$x | True if $x is not true |
PHP Array Operators
The PHP array operators are used to compare arrays:| Operator | Name | Example | Result |
|---|---|---|---|
| + | Union | $x + $y | Union of $x and $y (but duplicate keys are not overwritten) |
| == | Equality | $x == $y | True if $x and $y have the same key/value pairs |
| === | Identity | $x === $y | True if $x and $y have the same key/value pairs in the same order and of the same types |
| != | Inequality | $x != $y | True if $x is not equal to $y |
| <> | Inequality | $x <> $y | True if $x is not equal to $y |
| !== | Non-identity | $x !== $y | True if $x is not identical to $y |
Example
<?php
$x = array("a" => "red", "b" => "green");
$y = array("c" => "blue", "d" => "yellow");
$z = $x + $y; // union of $x and $y
var_dump($z);
var_dump($x == $y);
var_dump($x === $y);
var_dump($x != $y);
var_dump($x <> $y);
var_dump($x !== $y);
?>
$x = array("a" => "red", "b" => "green");
$y = array("c" => "blue", "d" => "yellow");
$z = $x + $y; // union of $x and $y
var_dump($z);
var_dump($x == $y);
var_dump($x === $y);
var_dump($x != $y);
var_dump($x <> $y);
var_dump($x !== $y);
?>
Conditional statements are used to perform different actions based on different conditions.
PHP Conditional Statements
Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this.In PHP we have the following conditional statements:
- if statement - executes some code only if a specified condition is true
- if...else statement - executes some code if a condition is true and another code if the condition is false
- if...elseif....else statement - selects one of several blocks of code to be executed
- switch statement - selects one of many blocks of code to be executed
PHP - The if Statement
The if statement is used to execute some code only if a specified condition is true.Syntax
if (condition)
{
code to be executed if condition is true;
}
{
code to be executed if condition is true;
}
Example
<?php
$t=date("H");
if ($t<"20")
{
echo "Have a good day!";
}
?>
$t=date("H");
if ($t<"20")
{
echo "Have a good day!";
}
?>
PHP - The if...else Statement
Use the if....else statement to execute some code if a condition is true and another code if the condition is false.Syntax
if (condition)
{
code to be executed if condition is true;
}
else
{
code to be executed if condition is false;
}
{
code to be executed if condition is true;
}
else
{
code to be executed if condition is false;
}
Example
<?php
$t=date("H");
if ($t<"20")
{
echo "Have a good day!";
}
else
{
echo "Have a good night!";
}
?>
$t=date("H");
if ($t<"20")
{
echo "Have a good day!";
}
else
{
echo "Have a good night!";
}
?>
PHP - The if...elseif....else Statement
Use the if....elseif...else statement to select one of several blocks of code to be executed.Syntax
if (condition)
{
code to be executed if condition is true;
}
elseif (condition)
{
code to be executed if condition is true;
}
else
{
code to be executed if condition is false; }
{
code to be executed if condition is true;
}
elseif (condition)
{
code to be executed if condition is true;
}
else
{
code to be executed if condition is false; }
Example
<?php
$t=date("H");
if ($t<"10")
{
echo "Have a good morning!";
}
elseif ($t<"20")
{
echo "Have a good day!";
}
else
{
echo "Have a good night!";
}
?>
$t=date("H");
if ($t<"10")
{
echo "Have a good morning!";
}
elseif ($t<"20")
{
echo "Have a good day!";
}
else
{
echo "Have a good night!";
}
?>
he switch statement is used to perform different actions based on different conditions.
This is how it works: First we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically. The default statement is used if no match is found.
In PHP, we have the following looping statements:
The example below first sets a variable $x to 1 ($x=1;). Then, the while loop will continue to run as long as $x is less than, or equal to 5. $x will increase by 1 each time the loop runs ($x++;):
The example below first sets a variable $x to 1 ($x=1;). Then, the do while loop will write some output, and then increment the variable $x with 1. Then the condition is checked (is $x less than, or equal to 5?), and the loop will continue to run as long as $x is less than, or equal to 5:
When a user fills out the form above and clicks on the submit button, the form data is sent to a PHP file, called "welcome.php":
"welcome.php" looks like this:
Output could be something like this:
The PHP $_GET and $_POST variables will be explained in the next chapters.
You should consider server validation if the user input will be inserted into a database. A good way to validate a form on the server is to post the form to itself, instead of jumping to a different page. The user will then get the error messages on the same page as the form. This makes it easier to discover the error.
Information sent from a form with the GET method is visible to everyone (it will be displayed in the browser's address bar) and has limits on the amount of information to send.
When the user clicks the "Submit" button, the URL sent to the server could look something like this:
The "welcome.php" file can now use the $_GET variable to collect form data (the names of the form fields will automatically be the keys in the $_GET array):
Note: This method should not be used when sending passwords or other sensitive information!
However, because the variables are displayed in the URL, it is possible to bookmark the page. This can be useful in some cases.
Note: The get method is not suitable for very large variable values. It should not be used with values exceeding 2000 characters.
The PHP switch Statement
Use the switch statement to select one of many blocks of code to be executed.Syntax
switch (n)
{
case label1:
code to be executed if n=label1;
break;
case label2:
code to be executed if n=label2;
break;
case label3:
code to be executed if n=label3;
break;
...
default:
code to be executed if n is different from all labels;
}
{
case label1:
code to be executed if n=label1;
break;
case label2:
code to be executed if n=label2;
break;
case label3:
code to be executed if n=label3;
break;
...
default:
code to be executed if n is different from all labels;
}
Example
<?php
$favcolor="red";
switch ($favcolor)
{
case "red":
echo "Your favorite color is red!";
break;
case "blue":
echo "Your favorite color is blue!";
break;
case "green":
echo "Your favorite color is green!";
break;
default:
echo "Your favorite color is neither red, blue, or green!";
}
?>
$favcolor="red";
switch ($favcolor)
{
case "red":
echo "Your favorite color is red!";
break;
case "blue":
echo "Your favorite color is blue!";
break;
case "green":
echo "Your favorite color is green!";
break;
default:
echo "Your favorite color is neither red, blue, or green!";
}
?>
PHP while loops execute a block of code while the specified condition is true.
PHP Loops
Often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal code-lines in a script, we can use loops to perform a task like this.In PHP, we have the following looping statements:
- while - loops through a block of code as long as the specified condition is true
- do...while - loops through a block of code once, and then repeats the loop as long as the specified condition is true
- for - loops through a block of code a specified number of times
- foreach - loops through a block of code for each element in an array
The PHP while Loop
The while loop executes a block of code as long as the specified condition is true.Syntax
while (condition is true)
{
code to be executed;
}
{
code to be executed;
}
Example
<?php
$x=1;
while($x<=5)
{
echo "The number is: $x <br>";
$x++;
}
?>
$x=1;
while($x<=5)
{
echo "The number is: $x <br>";
$x++;
}
?>
The PHP do...while Loop
The do...while loop will always execute the block of code once, it will then check the condition, and repeat the loop while the specified condition is true.Syntax
do
{
code to be executed;
}
while (condition is true);
{
code to be executed;
}
while (condition is true);
Example
<?php
$x=1;
do
{
echo "The number is: $x <br>";
$x++;
}
while ($x<=5)
?>
$x=1;
do
{
echo "The number is: $x <br>";
$x++;
}
while ($x<=5)
?>
Notice that in a do while loop the condition is tested AFTER executing the statements within the loop. This means that the do while loop would execute its statements at least once, even if the condition fails the first time.
The example below sets the $x variable to 6, then it runs the loop, and then the condition is checked:
Parameters:
For every loop iteration, the value of the current array element is assigned to $value and the array pointer is moved by one, until it reaches the last array element.
The following example demonstrates a loop that will output the values of the given array ($colors):
A function is a block of statements that can be used repeatadly in a program.
A function will not execute immediately when a page loads.
A function will be executed by a call to the function.
Note: A function name can start with a letter or underscore (not a number).
Tip: Give the function a name that reflects what the function does!
In the example below, we create a function named "writeMsg()". The opening curly brace ( { ) indicates the beginning of the function code and the closing curly brace ( } ) indicates the end of the function. The function outputs "Hello world!". To call the function, just write its name:
Arguments are specified after the function name, inside the parentheses. You can add as many arguments as you want, just seperate them with a comma.
The following example has a function with one argument ($fname). When the familyName() function is called, we also pass along a name (e.g. Jani), and the name is used inside the function, which outputs several different first names, but an equal last name:
Run example »
If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:
However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?
The solution is to create an array!
An array can hold many values under a single name, and you can access the values by referring to an index number.
In PHP, there are three types of arrays:
The index can be assigned automatically (index always starts at 0):
or the index can be assigned manually:
The following example creates an indexed array named $cars, assigns three elements to it, and then prints a text containing the array values:
There are two ways to create an associative array:
or:
The named keys can then be used in a script:
The following example sorts the elements of the $numbers array in ascending numerical order:
The following example sorts the elements of the $numbers array in descending numerical order:
The PHP superglobal variables are:
PHP stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable.
The example below shows how to use the super global variable $GLOBAL:
In the example above, since z is a variable present within the $GLOBALS array, it is also accessible form outside the function!
The example below shows how to use some of the elements in $_SERVER:
The following table lists the most important elements that can go inside $_SERVER:
The example below shows a form with an input field and a submit button. When a user submits the data by clicking on "Submit", the form data is sent to the file specified in the action attribute of the <form> tag. In this example, we point to this file itself for processing form data. If you wish to use another PHP file to process form data, replace that with the filename of your choice. Then, we can use the super global variable $_REQUEST to collect the value of the input field:
The example below shows a form with an input field and a submit button. When a user submits the data by clicking on "Submit", the form data is sent to the file specified in the action attribute of the <form> tag. In this example, we point to this file itself for processing form data. If you wish to use another PHP file to process form data, replace that with the filename of your choice. Then, we can use the super global variable $_POST to collect the value of the input field:
$_GET can also collect data sent in the URL.
Assume we have an HTML page that contains a hyperlink with parameters:
When a user clicks on the link "Test $GET", the parameters "subject" and "web" is sent to "test_get.php", and you can then acces their values in "test_get.php" with $_GET.
The example below shows the code in "test_get.php":
The example below sets the $x variable to 6, then it runs the loop, and then the condition is checked:
Example
<?php
$x=6;
do
{
echo "The number is: $x <br>";
$x++;
}
while ($x<=5)
?>
$x=6;
do
{
echo "The number is: $x <br>";
$x++;
}
while ($x<=5)
?>
PHP for loops execute a block of code a specified number of times.
The PHP for Loop
The for loop is used when you know in advance how many times the script should run.Syntax
for (init counter; test counter; increment counter)
{
code to be executed;
}
{
code to be executed;
}
- init counter: Initialize the loop counter value
- test counter: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.
- increment counter: Increases the loop counter value
Example
<?php
for ($x=0; $x<=10; $x++)
{
echo "The number is: $x <br>";
}
?>
for ($x=0; $x<=10; $x++)
{
echo "The number is: $x <br>";
}
?>
The PHP foreach Loop
The foreach loop works only on arrays, and is used to loop through each key/value pair in an array.Syntax
foreach ($array as $value)
{
code to be executed;
}
{
code to be executed;
}
The following example demonstrates a loop that will output the values of the given array ($colors):
Example
<?php
$colors = array("red","green","blue","yellow");
foreach ($colors as $value)
{
echo "$value <br>";
}
?>
$colors = array("red","green","blue","yellow");
foreach ($colors as $value)
{
echo "$value <br>";
}
?>
The real power of PHP comes from its functions; it has more than 1000 built-in functions.
PHP User Defined Functions
Besides the built-in PHP functions, we can create our own functions.A function is a block of statements that can be used repeatadly in a program.
A function will not execute immediately when a page loads.
A function will be executed by a call to the function.
Create a User Defined Function in PHP
A user defined function declaration starts with the word "function":Syntax
function functionName()
{
code to be executed;
}
{
code to be executed;
}
Tip: Give the function a name that reflects what the function does!
 | Remember that function names are case-insensitive. |
|---|
Example
<?php
function writeMsg()
{
echo "Hello world!";
}
writeMsg(); // call the function
?>
function writeMsg()
{
echo "Hello world!";
}
writeMsg(); // call the function
?>
PHP Function Arguments
Information can be passed to functions through arguments. An argument is just like a variable.Arguments are specified after the function name, inside the parentheses. You can add as many arguments as you want, just seperate them with a comma.
The following example has a function with one argument ($fname). When the familyName() function is called, we also pass along a name (e.g. Jani), and the name is used inside the function, which outputs several different first names, but an equal last name:
Example
<?php
function familyName($fname)
{
echo "$fname Refsnes.<br>";
}
familyName("Jani");
familyName("Hege");
familyName("Stale");
familyName("Kai Jim");
familyName("Borge");
?>
function familyName($fname)
{
echo "$fname Refsnes.<br>";
}
familyName("Jani");
familyName("Hege");
familyName("Stale");
familyName("Kai Jim");
familyName("Borge");
?>
The following example has a function with two arguments ($fname and $year):
Example
<?php
function familyName($fname,$year)
{
echo "$fname Refsnes. Born in $year <br>";
}
familyName("Hege","1975");
familyName("Ståle","1978");
familyName("Kai Jim","1983");
?>
function familyName($fname,$year)
{
echo "$fname Refsnes. Born in $year <br>";
}
familyName("Hege","1975");
familyName("Ståle","1978");
familyName("Kai Jim","1983");
?>
PHP Default Argument Value
The following example shows how to use a default parameter. If we call the function setHeight() without arguments it takes the default value as argument:Example
<?php
function setHeight($minheight=50)
{
echo "The height is : $minheight <br>";
}
setHeight(350);
setHeight(); // will use the default value of 50
setHeight(135);
setHeight(80);
?>
function setHeight($minheight=50)
{
echo "The height is : $minheight <br>";
}
setHeight(350);
setHeight(); // will use the default value of 50
setHeight(135);
setHeight(80);
?>
PHP Functions - Returning values
To let a function return a value, use the return statement:Example
<?php
function sum($x,$y)
{
$z=$x+$y;
return $z;
}
echo "5 + 10 = " . sum(5,15) . "<br>";
echo "7 + 13 = " . sum(7,13) . "<br>";
echo "2 + 4 = " . sum(2,4);
?>
function sum($x,$y)
{
$z=$x+$y;
return $z;
}
echo "5 + 10 = " . sum(5,15) . "<br>";
echo "7 + 13 = " . sum(7,13) . "<br>";
echo "2 + 4 = " . sum(2,4);
?>
An array stores multiple values in one single variable:
Example
<?php
$cars=array("Volvo","BMW","Toyota");
echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>
$cars=array("Volvo","BMW","Toyota");
echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>
Run example »
What is an Array?
An array is a special variable, which can hold more than one value at a time.If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:
$cars1="Volvo";
$cars2="BMW";
$cars3="Toyota";
$cars2="BMW";
$cars3="Toyota";
The solution is to create an array!
An array can hold many values under a single name, and you can access the values by referring to an index number.
Create an Array in PHP
In PHP, the array() function is used to create an array:array();
- Indexed arrays - Arrays with numeric index
- Associative arrays - Arrays with named keys
- Multidimensional arrays - Arrays containing one or more arrays
PHP Indexed Arrays
There are two ways to create indexed arrays:The index can be assigned automatically (index always starts at 0):
$cars=array("Volvo","BMW","Toyota");
$cars[0]="Volvo";
$cars[1]="BMW";
$cars[2]="Toyota";
$cars[1]="BMW";
$cars[2]="Toyota";
Example
<?php
$cars=array("Volvo","BMW","Toyota");
echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>
$cars=array("Volvo","BMW","Toyota");
echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>
Get The Length of an Array - The count() Function
The count() function is used to return the length (the number of elements) of an array:Loop Through an Indexed Array
To loop through and print all the values of an indexed array, you could use a for loop, like this:Example
<?php
$cars=array("Volvo","BMW","Toyota");
$arrlength=count($cars);
for($x=0;$x<$arrlength;$x++)
{
echo $cars[$x];
echo "<br>";
}
?>
$cars=array("Volvo","BMW","Toyota");
$arrlength=count($cars);
for($x=0;$x<$arrlength;$x++)
{
echo $cars[$x];
echo "<br>";
}
?>
PHP Associative Arrays
Associative arrays are arrays that use named keys that you assign to them.There are two ways to create an associative array:
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
$age['Peter']="35";
$age['Ben']="37";
$age['Joe']="43";
$age['Ben']="37";
$age['Joe']="43";
Example
<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
echo "Peter is " . $age['Peter'] . " years old.";
?>
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
echo "Peter is " . $age['Peter'] . " years old.";
?>
Loop Through an Associative Array
To loop through and print all the values of an associative array, you could use a foreach loop, like this:Example
<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
foreach($age as $x=>$x_value)
{
echo "Key=" . $x . ", Value=" . $x_value;
echo "<br>";
}
?>
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
foreach($age as $x=>$x_value)
{
echo "Key=" . $x . ", Value=" . $x_value;
echo "<br>";
}
?>
The elements in an array can be sorted in alphabetical or numerical order, descending or ascending.
PHP - Sort Functions For Arrays
In this chapter, we will go through the following PHP array sort functions:- sort() - sort arrays in ascending order
- rsort() - sort arrays in descending order
- asort() - sort associative arrays in ascending order, according to the value
- ksort() - sort associative arrays in ascending order, according to the key
- arsort() - sort associative arrays in descending order, according to the value
- krsort() - sort associative arrays in descending order, according to the key
Sort Array in Ascending Order - sort()
The following example sorts the elements of the $cars array in ascending alphabetical order:Example
<?php
$cars=array("Volvo","BMW","Toyota");
sort($cars);
?>
$cars=array("Volvo","BMW","Toyota");
sort($cars);
?>
Example
<?php
$numbers=array(4,6,2,22,11);
sort($numbers);
?>
$numbers=array(4,6,2,22,11);
sort($numbers);
?>
Sort Array in Descending Order - rsort()
The following example sorts the elements of the $cars array in descending alphabetical order:The following example sorts the elements of the $numbers array in descending numerical order:
Example
<?php
$numbers=array(4,6,2,22,11);
rsort($numbers);
?>
$numbers=array(4,6,2,22,11);
rsort($numbers);
?>
Sort Array in Ascending Order, According to Value - asort()
The following example sorts an associative array in ascending order, according to the value:Example
<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
asort($age);
?>
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
asort($age);
?>
Sort Array in Ascending Order, According to Key - ksort()
The following example sorts an associative array in ascending order, according to the key:Sort Array in Descending Order, According to Value - arsort()
The following example sorts an associative array in descending order, according to the value:Sort Array in Descending Order, According to Key - krsort()
The following example sorts an associative array in descending order, according to the key:Example
<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
krsort($age);
?>
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
krsort($age);
?>
Superglobals were introduced in PHP 4.1.0, and are built-in variables that are always available in all scopes.
PHP Global Variables - Superglobals
Several predefined variables in PHP are "superglobals", which means that they are always accessible, regardless of scope - and you can access them from any function, class or file without having to do anything special.The PHP superglobal variables are:
- $GLOBALS
- $_SERVER
- $_REQUEST
- $_POST
- $_GET
- $_FILES
- $_ENV
- $_COOKIE
- $_SESSION
PHP $GLOBAL
$GLOBAL is a PHP super global variable which is used to access global variables from anywhere in the PHP script (also from within functions or methods).PHP stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable.
The example below shows how to use the super global variable $GLOBAL:
Example
<?php
$x = 75;
$y = 25;
function addition()
{
$GLOBALS['z'] = $GLOBALS['x'] + $GLOBALS['y'];
}
addition();
echo $z;
?>
$x = 75;
$y = 25;
function addition()
{
$GLOBALS['z'] = $GLOBALS['x'] + $GLOBALS['y'];
}
addition();
echo $z;
?>
PHP $_SERVER
$_SERVER is a PHP super global variable which holds information about headers, paths, and script locations.The example below shows how to use some of the elements in $_SERVER:
Example
<?php
echo $_SERVER['PHP_SELF'];
echo "<br>";
echo $_SERVER['SERVER_NAME'];
echo "<br>";
echo $_SERVER['HTTP_HOST'];
echo "<br>";
echo $_SERVER['HTTP_REFERER'];
echo "<br>";
echo $_SERVER['HTTP_USER_AGENT'];
echo "<br>";
echo $_SERVER['SCRIPT_NAME'];
?>
echo $_SERVER['PHP_SELF'];
echo "<br>";
echo $_SERVER['SERVER_NAME'];
echo "<br>";
echo $_SERVER['HTTP_HOST'];
echo "<br>";
echo $_SERVER['HTTP_REFERER'];
echo "<br>";
echo $_SERVER['HTTP_USER_AGENT'];
echo "<br>";
echo $_SERVER['SCRIPT_NAME'];
?>
| Element/Code | Description |
|---|---|
| $_SERVER['PHP_SELF'] | Returns the filename of the currently executing script |
| $_SERVER['GATEWAY_INTERFACE'] | Returns the version of the Common Gateway Interface (CGI) the server is using |
| $_SERVER['SERVER_ADDR'] | Returns the IP address of the host server |
| $_SERVER['SERVER_NAME'] | Returns the name of the host server (such as www.w3schools.com) |
| $_SERVER['SERVER_SOFTWARE'] | Returns the server identification string (such as Apache/2.2.24) |
| $_SERVER['SERVER_PROTOCOL'] | Returns the name and revision of the information protocol (such as HTTP/1.1) |
| $_SERVER['REQUEST_METHOD'] | Returns the request method used to access the page (such as POST) |
| $_SERVER['REQUEST_TIME'] | Returns the timestamp of the start of the request (such as 1377687496) |
| $_SERVER['QUERY_STRING'] | Returns the query string if the page is accessed via a query string |
| $_SERVER['HTTP_ACCEPT'] | Returns the Accept header from the current request |
| $_SERVER['HTTP_ACCEPT_CHARSET'] | Returns the Accept_Charset header from the current request (such as utf-8,ISO-8859-1) |
| $_SERVER['HTTP_HOST'] | Returns the Host header from the current request |
| $_SERVER['HTTP_REFERER'] | Returns the complete URL of the current page (not reliable because not all user-agents support it) |
| $_SERVER['HTTPS'] | Is the script queried through a secure HTTP protocol |
| $_SERVER['REMOTE_ADDR'] | Returns the IP address from where the user is viewing the current page |
| $_SERVER['REMOTE_HOST'] | Returns the Host name from where the user is viewing the current page |
| $_SERVER['REMOTE_PORT'] | Returns the port being used on the user's machine to communicate with the web server |
| $_SERVER['SCRIPT_FILENAME'] | Returns the absolute pathname of the currently executing script |
| $_SERVER['SERVER_ADMIN'] | Returns the value given to the SERVER_ADMIN directive in the web server configuration file (if your script runs on a virtual host, it will be the value defined for that virtual host) (such as someone@w3scholls.com) |
| $_SERVER['SERVER_PORT'] | Returns the port on the server machine being used by the web server for communication (such as 80) |
| $_SERVER['SERVER_SIGNATURE'] | Returns the server version and virtual host name which are added to server-generated pages |
| $_SERVER['PATH_TRANSLATED'] | Returns the file system based path to the current script |
| $_SERVER['SCRIPT_NAME'] | Returns the path of the current script |
| $_SERVER['SCRIPT_URI'] | Returns the URI of the current page |
PHP $_REQUEST
PHP $_REQUEST is used to collect data after submitting an HTML form.The example below shows a form with an input field and a submit button. When a user submits the data by clicking on "Submit", the form data is sent to the file specified in the action attribute of the <form> tag. In this example, we point to this file itself for processing form data. If you wish to use another PHP file to process form data, replace that with the filename of your choice. Then, we can use the super global variable $_REQUEST to collect the value of the input field:
Example
<html>
<body>
<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
Name: <input type="text" name="fname">
<input type="submit">
</form>
<?php
$name = $_REQUEST['fname'];
echo $name;
?>
</body>
</html>
<body>
<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
Name: <input type="text" name="fname">
<input type="submit">
</form>
<?php
$name = $_REQUEST['fname'];
echo $name;
?>
</body>
</html>
PHP $_POST
PHP $_POST is widely used to collect form data after submitting an HTML form with method="post". $_POST is also widely used to pass variables.The example below shows a form with an input field and a submit button. When a user submits the data by clicking on "Submit", the form data is sent to the file specified in the action attribute of the <form> tag. In this example, we point to this file itself for processing form data. If you wish to use another PHP file to process form data, replace that with the filename of your choice. Then, we can use the super global variable $_POST to collect the value of the input field:
Example
<html>
<body>
<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
Name: <input type="text" name="fname">
<input type="submit">
</form>
<?php
$name = $_POST['fname'];
echo $name;
?>
</body>
</html>
<body>
<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
Name: <input type="text" name="fname">
<input type="submit">
</form>
<?php
$name = $_POST['fname'];
echo $name;
?>
</body>
</html>
PHP $_GET
PHP $_GET can also be used to collect form data after submitting an HTML form with method="get".$_GET can also collect data sent in the URL.
Assume we have an HTML page that contains a hyperlink with parameters:
<html>
<body>
<a href="test_get.php?subject=PHP&web=W3schools.com">Test $GET</a>
</body>
</html>
<body>
<a href="test_get.php?subject=PHP&web=W3schools.com">Test $GET</a>
</body>
</html>
The example below shows the code in "test_get.php":
Example
<html>
<body>
<?php
echo "Study " . $_GET['subject'] . " at " . $_GET['web'];
?>
</body>
</html>
<body>
<?php
echo "Study " . $_GET['subject'] . " at " . $_GET['web'];
?>
</body>
</html>
The PHP superglobals $_GET and $_POST are used to collect form-data.
PHP Form Handling
This chapter shows how to collect form-data from users using POST and GET method from various form controls.Example
The example below contains an HTML form with two input fields and a submit button:<html>
<body>
<form action="welcome.php" method="post">
Name: <input type="text" name="fname">
Age: <input type="text" name="age">
<input type="submit">
</form>
</body>
</html>
<body>
<form action="welcome.php" method="post">
Name: <input type="text" name="fname">
Age: <input type="text" name="age">
<input type="submit">
</form>
</body>
</html>
"welcome.php" looks like this:
<html>
<body>
Welcome <?php echo $_POST["fname"]; ?>!<br>
You are <?php echo $_POST["age"]; ?> years old.
</body>
</html>
<body>
Welcome <?php echo $_POST["fname"]; ?>!<br>
You are <?php echo $_POST["age"]; ?> years old.
</body>
</html>
Welcome John!
You are 28 years old.
You are 28 years old.
Form Validation
User input should be validated on the browser whenever possible (by client scripts). Browser validation is faster and reduces the server load.You should consider server validation if the user input will be inserted into a database. A good way to validate a form on the server is to post the form to itself, instead of jumping to a different page. The user will then get the error messages on the same page as the form. This makes it easier to discover the error.
In PHP, the predefined $_GET variable is used to collect values in a form with method="get".
The $_GET Variable
The predefined $_GET variable is used to collect values in a form with method="get"Information sent from a form with the GET method is visible to everyone (it will be displayed in the browser's address bar) and has limits on the amount of information to send.
Example
<form action="welcome.php" method="get">
Name: <input type="text" name="fname">
Age: <input type="text" name="age">
<input type="submit">
</form>
Name: <input type="text" name="fname">
Age: <input type="text" name="age">
<input type="submit">
</form>
http://www.w3schools.com/welcome.php?fname=Peter&age=37
Welcome <?php echo $_GET["fname"]; ?>.<br>
You are <?php echo $_GET["age"]; ?> years old!
You are <?php echo $_GET["age"]; ?> years old!
When to use method="get"?
When using method="get" in HTML forms, all variable names and values are displayed in the URL.Note: This method should not be used when sending passwords or other sensitive information!
However, because the variables are displayed in the URL, it is possible to bookmark the page. This can be useful in some cases.
Note: The get method is not suitable for very large variable values. It should not be used with values exceeding 2000 characters.
-------------------
In PHP, the predefined $_POST variable is used to collect values in a form with method="post".
The $_POST Variable
The predefined $_POST variable is used to collect values from a form sent with method="post".Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.
Note: However, there is an 8 MB max size for the POST method, by default (can be changed by setting the post_max_size in the php.ini file).
Example
<form action="welcome.php" method="post">
Name: <input type="text" name="fname">
Age: <input type="text" name="age">
<input type="submit">
</form>
Name: <input type="text" name="fname">
Age: <input type="text" name="age">
<input type="submit">
</form>
http://www.w3schools.com/welcome.php
Welcome <?php echo $_POST["fname"]; ?>!<br>
You are <?php echo $_POST["age"]; ?> years old.
You are <?php echo $_POST["age"]; ?> years old.
When to use method="post"?
Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.However, because the variables are not displayed in the URL, it is not possible to bookmark the page.
The PHP $_REQUEST Variable
The predefined $_REQUEST variable contains the contents of both $_GET, $_POST, and $_COOKIE.The $_REQUEST variable can be used to collect form data sent with both the GET and POST methods.
Example
Welcome <?php echo $_REQUEST["fname"]; ?>!<br>
You are <?php echo $_REQUEST["age"]; ?> years old.
You are <?php echo $_REQUEST["age"]; ?> years old.
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