Array Functions
PHP Manual

array_key_exists

Checks if the given key or index exists in the array

Description

bool array_key_exists ( mixed $key , array $array )

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.

See Also

  • isset
  • array_keys
  • in_array
  • property_exists