array_keys:返回数组中符合条件的键,组成为一个新的数组

$array = [
	'a' => 'abc',
	'aa' => 'abc',
	'aaa' => 'abc',
	'b' => 'bbc',
	'c' => 'cbc',
	'd' => 123,
	1 => '123',
	2 => 123
];

$arr = array_keys($array,'123',false);

echo '';
print_r($arr);

result:
Array
(
    [0] => d
    [1] => 1
    [2] => 2
)