小编am9*_*m90的帖子

我有这个登录页面,我在看Udemy的教程时写了它.他的代码工作正常,但在我的代码(相同)中,我有以下错误:

致命错误:在非对象上调用成员函数prepare()

这是代码:

<?php
    //$var = 'This is our first web app page';
    //echo $var;

    //Connection Variables:
    $dbhost = "localhost";
    $dbname = "graphic_db";
    $dbuser = "root";
    $dbpass = "root";

    //Connection to SQL:
    $conn = new PDO("mysql:host=$dbhost; dbname=$dbname", $dbuser, $dbpass);
    //Error messagin enabled:
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    //Adding a character set:
    $conn = exec("SET CHARACTER SET utf8mb4");

    $user = '';
    $pass = '';
    $sum = 0;
    $error_msg = "Please type a username and a password";
    if(isset($_POST['login_submit']))
    {
        //Start a session:
        session_start();
        $user = …