(PHP 4 >= 4.0.7, PHP 5)
array_key_exists — Checks if the given key or index exists in the 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.
key
Value to check.
search
An array with keys to check.
Returns TRUE on success or FALSE on failure.
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);
?>
Note:
For backward compatibility, the following deprecated alias may be used: key_exists()
Note:
For backward compatibility reasons, array_key_exists() will also return
TRUEifkeyis a property defined within an object given assearch. This behaviour should not be relied upon, and care should be taken to ensure thatsearchis an array.To check whether a property exists in an object, use property_exists().