(PHP 4 >= 4.1.0)
array_key_exists() returns TRUE if the given key is set in the array. key can be any value possible for an array index.
Example 1. array_key_exists() example
$search_array = array("first" => 1, "second" => 4); if (array_key_exists("first", $search_array)) { echo "The 'first' element is in the array"; }
Note: This name of this function is key_exists() in PHP version 4.0.6.
See also isset().