array_key_exists

(PHP 4 >= 4.1.0, PHP 5)

array_key_exists -- Checks if the given key or index exists in the array

Description

bool array_key_exists ( mixed key, array search )

array_key_exists() returns TRUE if the given key is set in the array. key can be any value possible for an array index. array_key_exists() also works on objects.

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";
}
?>

Note: The name of this function is key_exists() in PHP 4.0.6.

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);
?>

See also isset(), array_keys(), and in_array().