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How to check whether a variable is set or not using PHP ?

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We have given a variable and the task is to check whether a variable var is set or not in PHP. In order to do this task, we have the following methods in PHP:

Approach 1: Using isset() Method: The isset() method returns True if the variable is declared and its value is not equal to NULL.
 

Syntax:

bool isset( mixed $var [, mixed $... ] )

Example :

PHP

<?php
// PHP program to check whether 
// a variable is set or not 
    
$str = "GeeksforGeeks"
    
// Check value of variable is set or not 
if(isset($str)) { 
    echo "Value of variable is set"
else
    echo "Value of variable is not set"
?> 

                    

Output
Value of variable is set 

Approach 2: Using !empty() Method: The empty() method returns True if the variable is declared and its value is equal to empty and not a set.

Syntax:

bool empty( $var )

Example :

PHP

<?php
// PHP program to check whether 
// a variable is set or not 
    
$str = "GeeksforGeeks"
    
// Check value of variable is set or not 
if(!empty($str)) { 
    echo "Value of variable is set"
else
    echo "Value of variable is not set"
?> 

                    

Output
Value of variable is set 

Approach 3: Using !is_null() Method: The is_null() method returns True if the variable is declared and its value is equal to Null and not a set.

Syntax:

bool empty( $var )

Example :

PHP

<?php
// PHP program to check whether 
// a variable is set or not 
    
$str = "GeeksforGeeks"
    
// Check value of variable is set or not 
if(!is_null($str)) { 
    echo "Value of variable is set"
else
    echo "Value of variable is not set"
?>

                    

Output
Value of variable is set 



Last Updated : 01 Jun, 2020
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