function id($data){
    $host = 'localhost';
    $user = 'user';
    $password = '';
    $db_name = 'workers';
    $link=mysqli_connect($host, $user, $password, $db_name) or die(mysqli_error($link));
    mysqli_query($link, "SET NAMES 'utf8'");
    $query = "SELECT id FROM workers WHERE id>0  ";
    $result = mysqli_query($link, $query) or die( mysqli_error($link));
    for ($data = []; $row = mysqli_fetch_assoc($result); $data[] = $row);
    foreach ($data as $value):
       $str =implode('',$value);
    endforeach;
    return str;
}
function output_id($arr){
        var_dump((id($arr)));
}
output_id($arr);