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

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