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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.
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);
?>See Also
| isset() |
| array_keys() |
| in_array() |