How to convert multi-dimensional array into one-dimensional array in thinkphp?

Question

Array
(

[0] => Array
    (
        [user_id] => 1
    )

[1] => Array
    (
        [user_id] => 22
    )

)
I only want 1 and 22. How to change it into $a=array('1','22');

Answer 1

php版本要大于5.5.0
$userid_array = array_column($x,'userid');


php版本要大于5.4.0
$userid_array = array_map(function($item){return $item['userid'];},$x);

再低就for循环吧

Answer 2

array_map("current", two-dimensional array);

Answer 3

Do you need to query by column? Such a query can directly find the data of a one-digit array

$use_id = Db->table('table')->where([])->column('user_id');