array_keys()¶
array_keys() returns all keys, both integer and string, as a new numerically indexed array.
array_keys() has second parameter, which filters the keys by their corresponding value. Only the keys with the provided value are reported.
array_keys() has third parameter, which activate the identity comparison for the second argument, rather than the type-juggling default one.
array_keys() always returns a new array with numeric keys starting from 0. It preserves the order of appearance of the matching keys.
array_keys() returns an empty array, when provided with an empty array. It also works with multi-dimensional arrays, but only scans the first level.
array_keys() does not work on objects. It may work, with caveats, by casting the object to array with (array).
array_keys() is a complement to array_values, which returns only the values. It is the partial contrary to array_combine().
<?php
$array = [
'name' => 'Alice',
10 => 'ten',
'age' => 25,
'active'=> true
];
$keys = array_keys($array);
// Result: ['name', 10, 'age', 'active']
?>
See also PHP array_keys: How to Extract Keys in Arrays with Examples.
Related : Multidimensional Array, Cast Operator, Comparison, Index For Arrays, array_values(), array_combine(), array_unique()
