array_key_exists
(PHP 4 >= 4.0.7, PHP 5)
array_key_exists — Checks if the given key or index exists in the array
Description
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.
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, 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 asarray. This behaviour should not be relied upon, and care should be taken to ensure thatarrayis an array.To check whether a property exists in an object, use property_exists().
See Also
- isset() - Determine if a variable is set and is not NULL
- array_keys() - Return all the keys or a subset of the keys of an array
- in_array() - Checks if a value exists in an array
- property_exists() - Checks if the object or class has a property
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Коментарии
When you want to check multiple array keys:
<?php
$array = [];
$array['a'] = '';
$array['b'] = '';
$array['c'] = '';
$array['d'] = '';
$array['e'] = '';
// all given keys a,b,c exists in the supplied array
var_dump(array_keys_exists(['a','b','c'], $array)); // bool(true)
function array_keys_exists(array $keys, array $array): bool
{
$diff = array_diff_key(array_flip($keys), $array);
return count($diff) === 0;
}
In PHP7+ to find if a value is set in a multidimensional array with a fixed number of dimensions, simply use the Null Coalescing Operator: ??
So for a three dimensional array where you are not sure about any of the keys actually existing
<?php
// instead of:
$exists = array_key_exists($key1, $arr) && array_key_exists($key2, $arr[$key1]) && array_key_exists($key3, $arr[$key1][$key2]) ;
// use:
$exists = array_key_exists($key3, $arr[$key1][$key2]??[]) ;
?>