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- Last Updated :21 Jun, 2022
The $x (single dollar) is the normal variable with the name x that stores any value like string, integer, float, etc. The $$x (double dollar) is a reference variable that stores the value which can be accessed by using the $ symbol before the $x value. These are called variable variables in PHP.
Variable Variables:- Variable variables are simply variables whose names are dynamically created by another variable’s value.
From the given figure below, it can be easily understood that:
- $x stores the value “Geeks” of String type.
- Now reference variable $$x stores the value “for Geeks” in it of String type.
So, the value of “for geeks” can be accessed in two ways which are listed below:
- By using the Reference variable directly. Example: echo $$x;
- By using the value stored at variable $x as a variable name for accessing the “for Geeks” value. Example: echo $Geeks; which will give output as “for Geeks” (without quote marks).
Examples:
Input : $x = "Geeks"; $$x = for Geeks; echo "$x "; echo "$$x;"; echo $Geeks;Output : Geeks for Geeks for GeeksInput : $x = "Rajnish"; $$x = "Noida"; echo "$x lives in " . $Rajnish;Output : Rajnish lives in Noida
Below are examples illustrating the use of $ and $$ in PHP:
Example-1:
php
<?php
// Declare variable and initialize it
$x = "Geeks";
// Reference variable
$$x = "GeeksforGeeks";
// Display value of x
echo $x . "\n";
// Display value of $$x ($Geeks)
echo $$x . "\n";
// Display value of $Geeks
echo "$Geeks";
?>
Output:
GeeksGeeksforGeeksGeeksforGeeks
Example-2:
php
<?php
// Declare variable and initialize it
$var = "Geeks";
// Reference variable
${$var}="GeeksforGeeks";
// Use double reference variable
${${$var}}="computer science";
// Display the value of variable
echo $var . "\n";
echo $Geeks . "\n";
echo $GeeksforGeeks . "\n";
// Double reference
echo ${${$var}}. "\n";
?>
Output:
GeeksGeeksforGeekscomputer sciencecomputer science
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