The isset() function is an inbuilt function in PHP which is used to determine if the variable is declared and its value is not equal to NULL.
Syntax:
bool isset( mixed $var [, mixed $... ] )
Parameters: This function accept one or more parameter as mentioned above and described below:
- $var: It contains the variable which need to check.
- $…: It contains the list of other variables.
Return Value: It returns TRUE if var exists and its value not equal to NULL and FALSE otherwise.
Below examples illustrate the isset() function in PHP:
Example 1:
<?php   $str = "neveropen";   // Check value of variable is set or not if(isset($str)) {     echo "Value of variable is set"; } else {     echo "Value of variable is not set"; }   $arr = array();   // Check value of variable is set or not if( !isset($arr[0]) ) {     echo "\nArray is Empty"; } else {     echo "\nArray is not empty"; }   ?> |
Output:
Value of variable is set Array is Empty
Output:
Example 2:
<?php   $num = 21; var_dump(isset($num));   $arr = array(         "a" => "Welcome",         "b" => "to",         "c" => "neveropen"    );   var_dump(isset($arr["a"])); var_dump(isset($arr["b"])); var_dump(isset($arr["c"])); var_dump(isset($arr["Geeks"]));   ?> |
Output:
bool(true) bool(true) bool(true) bool(true) bool(false)
