PHP Manual: Checks if the given key or index exists in the array

Description

bool array_key_exists(stringintfloatboolresourcenull $key, array $array)

array_key_exists returns true if the given key is set in the array. key can be any value possible for an array index.

Parameters

key: Value to check.
array: An array with keys to check.

Return Values

Returns true on success or false on failure.

Note:
array_key_exists will search for the keys in the first dimension only. Nested keys in multidimensional arrays will not be found.

Changelog

Version	Description
8.0.0	The `key` parameter now accepts `bool`, `float`, `int`, `null`, `resource`, and `string` as arguments.

Examples

Example #1 array_key_exists example

<?php
$search_array = array('first' => 1, 'second' => 4);
if (array_key_exists('first', $search_array)) {
    echo "The 'first' element is in the array";
}
?>

Example #2 array_key_exists vs isset

isset does not return true for array keys that correspond to a null value, while array_key_exists does.

<?php
$search_array = array('first' => null, 'second' => 4);

// returns false
isset($search_array['first']);

// returns true
array_key_exists('first', $search_array);
?>

Notes

Note:
For backward compatibility reasons, array_key_exists will also return true if key is a property defined within an object given as array. This behaviour is deprecated as of PHP 7.4.0, and removed as of PHP 8.0.0.

To check whether a property exists in an object, property_exists should be used.

array_key_exists