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PHP Variables

Last updated: April 6, 2026
Minimum PHP Version: PHP 5.0+

Overview

In PHP, variables store all pieces of data—numbers, characters, strings, and everything else. Variables are the fundamental building blocks of any PHP program, used to hold and manipulate data throughout your application.

When to Use

  • Storing values for later use
  • Passing data between functions
  • Building data structures (arrays, objects)
  • Managing application state
  • Creating reusable code

Basic Example

<?php
$name = "John";
$age = 30;
$score = 95.5;
$isActive = true;

echo $name;  // Output: John
echo $age;   // Output: 30
?>

Advanced Example

<?php
// Type declarations (PHP 7.0+)
function addNumbers(int $a, int $b): int {
    return $a + $b;
}

// Strict types (PHP 7.0+)
declare(strict_types=1);

$x = 10;
$y = 20;
$result = addNumbers($x, $y);

echo "Result: $result";  // Output: Result: 30
?>

PHP Version Support

Introduced: PHP 3.0
Minimum Required: PHP 5.0+
Type Hints: PHP 5.0+
Strict Types: PHP 7.0+

See Also

In PHP, we store all pieces of data -- numbers, characters, strings, everything -- as objects, and we refer to these objects using variables. As a simple case, we can assign a variable a value using the assignment operator, which is the "equals" sign.

Creating (Declaring) PHP Variables

In PHP, a variable starts with the $ sign, followed by the name of the variable:

Remember that variables are case-sensitive!

<?php
$txt = "Hello world!"; //No difference between "" and ''
$x = 5;
$y = 10.5;
?>
After the execution of the statements above, the variable $txt will hold the value Hello world!, the variable $x will hold the value 5, and the variable $y will hold the value 10.5.

Note: When you assign a text value to a variable, put quotes around the value.

Note: Unlike other programming languages, PHP has no command for declaring a variable. It is created the moment you first assign a value to it.

Rules for PHP variables:

  • A variable starts with the $ sign, followed by the name of the variable
  • A variable name must start with a letter or the underscore character
  • A variable name cannot start with a number
  • A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
  • Variable names are case-sensitive ($age and $AGE are two different variables)

Output Variables

The PHP echo statement is often used to output data to the screen.

The following example will show how to output text and a variable:

<?php
$txt = "phpTutorial";
echo "I love $txt!";
?>

Tools for understanding strange objects

var_dump() function

  • var_dump() displays structured information about one or more expressions that includes its type and value. Arrays and objects are explored recursively with values indented to show structure.

<!DOCTYPE html>
<html>
<body>

<?php  
$x = 5985;
var_dump($x);
?>  

</body>
</html>

int(5985)

  • print_r() displays the value of a variable, in a human-readable format.

<?php
$a = array("red", "green", "blue");
print_r($a);

echo "<br>";

$b = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
print_r($b);
?>

Array ( [0] => red [1] => green [2] => blue )
Array ( [Peter] => 35 [Ben] => 37 [Joe] => 43 )

NULL

The null type is PHP's unit type, i.e. it has only one value: null.

Undefined, and unset() variables will resolve to the value null.

There is only one value of type null, and that is the case-insensitive constant null. 

<?php
$var = NULL;       
?>