面向对象和过程化Mysqli帮助？

Question

我asked a question earlier和一个用户说，看起来我是oddly mixing the OO and procedural style usage of mysqli，我应该坚持一个或另一个。

有没有人可以告诉我我的代码到底出了什么问题，以及我的代码在面向对象和过程化形式下应该是什么样子。我现在有点好奇，因为我的代码似乎对我来说是有效的，但话说回来，我对PHP和MySQL还是相当陌生的，我想学习正确的方法。

下面是代码。

// Query member data from the database and ready it for display
$mysqli = new mysqli("localhost", "root", "", "sitename");
$dbc = mysqli_query($mysqli,"SELECT users.*, categories.*, users_categories.* FROM users_categories INNER JOIN users ON users_categories.user_id = users.user_id INNER JOIN categories ON users_categories.category_id = categories.id WHERE users_categories.user_id=3");

if (!$dbc) {
    // There was an error...do something about it here...
    print mysqli_error($mysqli);
}

Answer 1

// Query member data from the database and ready it for display
$mysqli = new mysqli("localhost", "root", "", "sitename");
$dbc = $mysqli->query("SELECT users.*, categories.*, users_categories.* FROM     users_categories INNER JOIN users ON users_categories.user_id = users.user_id INNER JOIN categories ON users_categories.category_id = categories.id WHERE users_categories.user_id=3");

if (!$dbc) {
    // There was an error...do something about it here...
    print $mysqli->error();
}

我不认为你应该以这种方式开始学习oop。我推荐你http://php.net/manual/en/oop5.intro.php

Answer 2

我在过去用过这个，不知道它是否有帮助，因为这不是你问题的真正答案，但可能有用。

    <?php // cnxVars
    class cnxVars {

 private $host = "localhost";
 private $host_un = "username";
 private $host_pass = "test123";
 private $host_db = "si";

 public function cnx() { // Connect to MySQL
  $this->cnx = mysql_connect($this->host, $this->host_un, $this->host_pass) or mysql_error(); }

 public function db() { // Select DB
  return mysql_select_db($this->host_db, $this->cnx) or mysql_error(); }


    } // End cnxVars ?>

然后你可以这样做

$mysql = new cnxVars();
$mysql->cnx();
$mysql->db();