这里对php非常陌生，我一直在研究如何对sql连接使用参数化查询。但是我看到的每一件事都让我觉得我每次都需要更改相同的值，这样参数化查询才会有用。有没有办法缩小我目前使用参数化查询所做的查询？我读错这些东西了吗？
我可能对php不太熟悉，但我知道，总的来说，这段代码相当糟糕。我不喜欢有多个select*查询，然后通过关联引用所需的字段。但我也有不这样做的问题。有人能快速看一眼这个，把我推向正确的方向吗？我已经准备好被称为哑巴了，所以带上它谢谢。

<?php
    session_start();

    // initializing variables
    $username = "";
    $email    = "";
    $errors = array(); 

    // connect to the database
    $db = mysqli_connect('db_server', 'db_user', 'db_pw', 'db_name');

    // REGISTER USER
    if (isset($_POST['register-submit'])) {
      // receive all input values from the form
      $username = mysqli_real_escape_string($db, $_POST['reg_username']);
      $email = mysqli_real_escape_string($db, $_POST['reg_email']);
      $password_1 = mysqli_real_escape_string($db, $_POST['reg_password_1']);
      $password_2 = mysqli_real_escape_string($db, $_POST['reg_password_2']);
      $actcode  = mysqli_real_escape_string($db, $_POST['reg_actcode']);

      // form validation: ensure that the form is correctly filled ...
      // by adding (array_push()) corresponding error unto $errors array
      if (empty($username)) { array_push($errors, "Username is required"); }
      if (empty($email)) { array_push($errors, "Email is required"); }
      if (empty($password_1)) { array_push($errors, "Password is required"); }
      if ($password_1 != $password_2) { array_push($errors, "The two passwords do not match"); }
      if ($actcode != "tobecaps") { array_push($errors, "Wrong activation code"); }

      // first check the database to make sure 
      // a user does not already exist with the same username and/or email
      $user_check_query = "SELECT * FROM `users` WHERE user_name='$username' OR user_email='$email' LIMIT 1";
      $result = mysqli_query($db, $user_check_query);
      $user = mysqli_fetch_assoc($result);

      if ($user) { // if user exists
        if ($user['user_name'] === $username) {
          array_push($errors, "Username already exists");
        }

        if ($user['user_email'] === $email) {
          array_push($errors, "email already exists");
        }
      }

      // Finally, register user if there are no errors in the form
      if (count($errors) == 0) {
        $password = md5($password_1);//encrypt the password before saving in the database

        $query1 = "INSERT INTO `users` (user_name, user_email, user_password, user_register_time) VALUES('$username', '$email', '$password', 'time()')";
        mysqli_query($db, $query1);

        $query2 = "SELECT * FROM `users` WHERE user_name='$username' LIMIT 1";
        $result2 = mysqli_query($db, $query2);
        $new_user = mysqli_fetch_assoc($result2);
        $user_id = $new_user['user_id'];

        $planet_found = false;

        while (!$planet_found) {
            $galaxy = mt_rand(1, 1);
            $system = mt_rand(1, 15);
            $planet = mt_rand(1, 15);

            $query3 = "SELECT * FROM `planets` WHERE planet_galaxy='$galaxy' AND planet_system='$system' AND planet_planet='$planet' LIMIT 1";
            $result3 = mysqli_query($db, $query3);
            $planet_result = mysqli_fetch_assoc($result3);

            if (!$planet_result) {
                $planet_found = true;
            }
        }

        $query4  = "INSERT INTO `planets` (planet_user_id, planet_galaxy, planet_system, planet_planet) VALUES('$user_id', '$galaxy', '$system', '$planet')";
        $result4 = mysqli_query($db, $query4);

        $query5  = "SELECT * FROM `planets` WHERE planet_user_id='$user_id' LIMIT 1";
        $result5 = mysqli_query($db, $query5);
        $planets_info = mysqli_fetch_assoc($result5);
        $planets_id = $planets_info['planet_id'];

        $query6  = "UPDATE `users` SET user_home_planet_id='$planets_id', user_galaxy='$galaxy', user_system='$system', user_planet='$planet' WHERE user_id='$user_id'";
        $result6 = mysqli_query($db, $query6);

        //update tables with new ids here

        $_SESSION['username']   = $username;
        $_SESSION['success']    = "You are now logged in";
        header("Location: ../");
      } else {
          header("Location: ../");
      }
    }       
?>

是的，这是目前的工作；但我相信我能打破它。欢迎提出任何建议。
通常，代码会检查用户是否存在。如果没有，它会将它们添加到用户数据库中，然后为它们创建一个随机的生存位置。