对两个准备好的语句使用相同的MySql连接

Question

所以我的PHP代码遇到了问题，我试图运行两个准备好的语句，这两个语句都是用相同的$mysqli对象“prepared”的。

        require 'database.php';
        $mysqli = new mysqli($database_host, $database_user, $database_pass, $database_name);

        /*First check if there is already a preference record for this user
          with this particular course.*/
        $query = "SELECT * FROM timetablePrefs WHERE username=? AND courseID=?";
        $stmt = $mysqli->prepare($query);
        foreach ($courseList as $key => $value)
        {
            $stmt->bind_param("ss", $username, $key);
            $stmt->execute();
            if (($stmt->num_rows) === 1)
                continue;
            else
            {
                $query = "INSERT INTO timetablePrefs (username, courseID, hexColour, hidden) ";
                $query .= "VALUES (?, ?, ?, 0)";
                $prepared = $mysqli->prepare($query);
                $prepared->bind_param("sss", $username, $key, "#FFFFFF");
                if (!($prepared->execute()))
                    print("Sorry couldnt change your colour preferences.");
                $prepared->close();
            }
        }
        $stmt->close();
        $mysqli->close();

我可能错过了什么；你能同时运行两个吗？如有任何帮助，我们将不胜感激！如有任何问题，请询问；）

Answer 1

1. 获取实际错误
2. 来解决它。从错误中可以看出，前面的查询有结果挂起。需要存储它们