PHP | isset() Function

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:

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<?php
  
$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";
}
  
$arr = array();
  
// Check value of variable is set or not
if( !isset($arr[0]) ) {
    echo "\nArray is Empty";
}
else {
    echo "\nArray is not empty";
}
  
?>

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Output:

Value of variable is set
Array is Empty

Output:

Example 2:

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<?php
  
$num = 21;
var_dump(isset($num));
  
$arr = array(
        "a" => "Welcome",
        "b" => "to",
        "c" => "GeeksforGeeks"
    );
  
var_dump(isset($arr["a"]));
var_dump(isset($arr["b"]));
var_dump(isset($arr["c"]));
var_dump(isset($arr["Geeks"]));
  
?>

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Output:

bool(true)
bool(true)
bool(true)
bool(true)
bool(false)

Reference: https://www.php.net/manual/en/function.isset.php




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