PHP Reference

Reference in PHP allows two different PHP variables to write to the same value, for example

$reference_var1 = &$reference_var2;

Here both the variable, that is, $reference_var1 and $reference_var2 are equal.

You can say, both variable point to the same place.

PHP Reference Example

Let's take an example that demonstrates reference in PHP.

<html>
<head>
   <title>PHP Reference Example</title>
</head>
<body>
<?php
   $num1 = 10;
   $num2 = &$num1;
   $sum = $num1 + $num2;
   echo $sum;
?>
</body>
</html>

Below is the sample output produced by the above reference example code in PHP.

Main Use of Reference in PHP

If you assign the reference of any variable say $first_ref_var to a another variable say $second_ref_var, then if you change the value of variable $first_ref_var, the $second_ref_var's value will also be changed automatically, as you have assigned the reference of that variable.

Let's take another example to understand about the main use of reference in PHP.

<html>
<head>
   <title>Reference example in PHP</title>
</head>
<body>
<?php
   echo "With Reference:<br/>";
   // initialize first variable with value
   $num1 = 10;
   // initialize the reference of first variable to second variable
   $num2 = &$num1;
   $sum = $num1 + $num2;
   echo $sum;
   echo "<br/>";
   // change the value of first variable
   $num1 = 20;
   echo $num1;
   echo "<br/>";
   // you will see, the value of second variable will also be changed
   // this is the benefit of using reference in PHP
   echo $num2;
   echo "<hr/>";
   
   echo "Without Reference:<br/>";
   $var1 = 10;
   $var2 = $var1;
   $add = $var1 + $var2;
   echo $add;
   $var1 = 20;
   echo "<br/>";
   echo $var1;
   echo "<br/>";
   echo $var2;
?>
</body>
</html>

Here is the sample output of the above reference example in PHP.

PHP Online Test

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