Online PHP editor | refs for Biok8

<?php if (!function_exists('array_find_key')) { function array_find_key(array $array, callable $callback) { foreach ($array as $key => $value) { if ($callback($value, $key)) { return $key; } } return null; } } $testcase = [ "['foo', 1]" => ['foo', 1], "['foo' => 1]" => ['foo' => 1], "['foo' => 'bar']" => ['foo' => 'bar'], ]; echo json_encode(array_map(fn ($a) => array_find_key($a, fn ($v) => is_int($v)), $testcase), JSON_PRETTY_PRINT);