array_key_exists Checks if the given key or index exists in the array boolarray_key_exists mixedkey arraysearch 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. 1, 'second' => 4); if (array_key_exists('first', $search_array)) { echo "The 'first' element is in the array"; } ?> ]]> The name of this function is key_exists in PHP 4.0.6. isset does not return &true; for array keys that correspond to a &null; value, while array_key_exists does. null, 'second' => 4); // returns false isset($search_array['first']); // returns true array_key_exists('first', $search_array); ?> ]]> See also isset, array_keys, and in_array.