MySQL查询Mysqli查询

Question

你好，我想将以下代码迁移到mysqli。请帮助，这是登录功能。第一个功能从数据库中获取user_id，而第二个功能检查username和password是否从user_id匹配了该用户。

function user_id_from_usernam­e($username){
   $username = sanitize($username);
   return mysql_result(mysql_query("SELECT `user_id` FROM `users` WHERE `username` = '$username'"), 0, 'user_id');
}
function login($username, $password){
  $user_id = user_id_from_username($username);
  $username = sanitize($username);
  $password = md5($password);
  $query = mysql_query("SELECT COUNT(`user_id`) FROM `users` WHERE `username` = '$username' AND `password` = '$password'");
  return  ( mysql_result($query­, 0) == 1)? $user_id : false;
}

Answer 1

mysqli_query的正确查询形式是：

mysqli_query($connection_variable,"SELECT COUNT(`user_id`) FROM `users` WHERE `username` = '$username' AND `password` = '$password'");