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array_key_exists

Checks if the given key or index exists in the array (PHP 4 >= 4.0.7, PHP 5)
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.

Parameters

key

Value to check.

search

An array with keys to check.

Return Values

Returns TRUE on success or FALSE on failure.

Examples

Example 254. 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 255. 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);
?>