PHP Variables, Easy To Learn Variables Tutorial in PHP

PHP Variables

PHP Variables are used for storing data such as numeric values, characters, character strings etc. All PHP variable names must be pre-fixed with a ( $). It is prefix which informs the PHP pre-processor that it is dealing with a variable name must start with a letter or the underscore character. A variable name cannot start with a number. Variable names are case-sensitive they are ($var and $VAR are two different variables).

Syntax of declaring a PHP valid and invalid variable names :

$varName // valid

$_varName // valid

$__varname // valid

$var_name // valid

$varName21 // valid

$_var-Name // invalid contains non alphanumeric character (-)

$_9Var // invalid - underscore must be followed by a letter

$99Var // invalid - must begin with a letter or underscore

Example :

<!DOCTYPE html>
<html>
<head>
<title>PHP Variables</title>
</head>

<body>

	<?php
        $ftl = "www.freetimelearning.com";
        echo "My Website is : " . $ftl;
    ?>
    <p>(or)</p>
    <?php
        echo "$ftl";
    ?>
    <p>(or)</p>
    <?php
        echo $ftl;
    ?>
    
</body>
</html>

Output :

PHP Variable - case sensitive

In PHP, variable names are case sensitive. So variable name "ftl" is different from fTl, ftl, FTL etc.

<!DOCTYPE html>
<html>
<head>
<title>PHP Case Sensitivity</title>
</head>
<body>

<h4>PHP Case Sensitivity</h4>
<?php
$ftl = "www.freetimelearning.com";
echo "My Website is : " . $ftl . "<br><br>";
echo "My Website is : " . $fTl . "<br><br>";
echo "My Website is : " . $FTL;
?>
    
</body>
</html>

Output :

PHP is a Loosely typed language

In other languages such as C, C++, and Java, the programmer must declare the name and type of the variable before using it.

The PHP automatically converts the variable to its correct data type.

PHP variable($) and variables($$)

The $var it is a normal variable with the name var that stores any value like string, integer, float, etc. And the $$var is a variable that stores the value of the $variable inside it.

<!DOCTYPE html>
<html>
<head>
	<title>PHP variable($) and variables($$)</title>
</head>

<body>
	<?php  
	$name = "FreeTimeLearning";  
	$$name = "www.freetimelearning.com";  
	echo $name."<br/>";  
	echo $$name."<br/>";  
	echo $FreeTimeLearning;  
	?>   
</body>
</html>

Output :

In the above example, we have assigned a value to the variable name as FreeTimeLearning. Value of reference variable $$name is assigned as www.freetimelearning.com.

Now we have printed the values $name, $$anme and a string.

Another Example

<!DOCTYPE html>
<html>
<head>
	<title>PHP variable($) and variables($$)</title>
</head>

<body>
	<?php
		$x = "FTL";
		$$x = "900";
		echo $x."<br/>";
		echo $$x."<br/>";
		echo $FTL;
	?> 
</body>
</html>

Output :

In the above example, we have assigned a value to the variable x as FTL. Value of reference variable $$x is assigned as 900.

Now we have printed the values $x, $$x and $FTL.

Example

<!DOCTYPE html>
<html>
<head>
	<title>PHP variable($) and variables($$)</title>
</head>

<body>  
    <?php  
	$name="FreeTimeLearning";  
	${$name}="freetimelearn";  
	${${$name}}="www.freetimelearning.com";  
	echo $name. "<br>";  
	echo ${$name}. "<br>";  
	echo $FreeTimeLearning. "<br>";  
	echo ${${$name}}. "<br>";  
	echo $freetimelearn. "<br>";  
	?>  
</body>
</html>

Output :

In the above example, we have assigned a value to the variable name FreeTimeLearning. Value of reference variable ${$name} is assigned as freetimelearn and ${${$name}} as www.freetimelearning.com.

Now we have printed the values as $name, ${$name}, $FreeTimeLearning, ${${$name}} and $freetimelearn.

PHP Variable Scopes

In PHP, variables can be declared anywhere in the script. We declare the variables for a particular scope.

There are three different types of variable scopes.

local
global
static

Global and Local Scope

The local scope where variables are created and accessed inside a function and global scope where variables are created and accessed outside a function.

<!DOCTYPE html>
<html>
<head>
	<title>Global and Local Scope</title>
</head>
<?php
//don't disply erroes
error_reporting(0);
?>
<body>
	<?php  
		//global scope  
		$x = 18;  
		function Sample()  
		{  
		//local scope  
		$y=90;  
		echo "The x value is :  $x "."<br /><br />";  
		echo "The y value is  :  $y"."<br />";  
		}  
		Sample();  
		echo "The x value is :  $x"."<br /><br />";  
		echo "The y value is  :  $y";  
	?>   
</body>
</html>

Output :

The global keyword

The global keyword is used to access a global variable from within a function.

To use these variables inside a function the variables must be declared global in that function. To do this we use the global keyword before the variables. They are following example :

<!DOCTYPE html>
<html>
<head>
	<title>Global Keyword</title>
</head>

<body>
	<?php  
		$x=3;  
		$y=6;  
		$z=9;  
		$xyz=0;  
		function multiple()  
		{  
		global $x, $y, $z, $xyz;  
		$xyz=$x*$y*$z;  
		}  
		multiple();  
		echo $xyz;  
	?>  
</body>
</html>

Output :

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. To do this, use the static keyword when you first declare the variable :

<!DOCTYPE html>
<html>
<head>
	<title>Static Keyword</title>
</head>

<body>
	<?php
		function Sample() {
			static $x = 3;
			echo $x;
			$x++;
		}
		
		Sample();
		echo "<br>";
		Sample();
		echo "<br>";
		Sample();
	?> 
</body>
</html>

Output :

PHP Tutorial