(PHP 4 >= 4.0.7, PHP 5, PHP 7)
array_key_exists — Checks if the given key or index exists in the array
array_key_exists ( string|int $key , array $array ) : bool
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.
array
An 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.
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 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().
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https://www.php.net/manual/en/function.array-key-exists.php