W3cubDocs

/PHP

array_key_exists

(PHP 4 >= 4.0.7, PHP 5, PHP 7)

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

Description

array_key_exists ( string|int $key , array $array ) : bool

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.

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 should not be relied upon, and care should be taken to ensure that array is an array.

To check whether a property exists in an object, use property_exists().