(PHP 4 >= 4.0.7, PHP 5, PHP 7, PHP 8)
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.
keyValue to check.
arrayAn array with keys to check.
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.
| Version | Description |
|---|---|
| 8.0.0 |
The key parameter now accepts
bool, float, int,
null, resource, and
string as arguments.
|
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 reasons, array_key_exists() will also return
trueifkeyis a property defined within an object given asarray. This behaviour is deprecated as of PHP 7.4.0, and removed as of PHP 8.0.0.To check whether a property exists in an object, property_exists() should be used.
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]??[]) ;
?>