收到“找不到PDO类"错误

我有一个简单的即将推出"页面，在该页面上可以订阅要插入到mysql数据库中的电子邮件.

I have a simple 'Coming Soon' page on which I take subscribing emails which I intend to insert into a mysql database.

我以前运行过代码，但是现在在1-2周后又回到了代码上，似乎有一些问题.

I had the code running before, but now coming back to it 1-2 weeks later, there seem to be some problems.

基本上只涉及2个文件:index.html和subscribe.php. index.html实际上是即将推出"页面，它调用subscribe.php将电子邮件实际插入数据库中，前提是该电子邮件有效，不是重复的，等等.

Basically there are only 2 files involved: index.html and subscribe.php. index.html is the actually 'Coming Soon' page, and it calls subscribe.php to actually insert the email into database, provided its a valid email, is not a duplicate, etc ..

subscribe.php的代码如下.这真的是一个非常简单的代码.

The code for subscribe.php is given below. Its a very simple code really.

这不是以前起作用的！但是，现在似乎在使用PDO的行出现找不到PDO类..."错误:

Do not that this WAS working before ! However now there seems to be a 'Class PDO not found ...' error coming at the line where PDO is being used:

<?php

function isValidEmail( $email = null )
{
    return preg_match( "/^
    [\d\w\/+!=#|$?%{^&}*`'~-]
    [\d\w\/\.+!=#|$?%{^&}*`'~-]*@
    [A-Z0-9]
    [A-Z0-9.-]{0,61}
    [A-Z0-9]\.
    [A-Z]{2,6}$/ix", $email );
}

try {
    // Connect to the SQLite Database.
    $db = new PDO('mysql:host=hostnamehere;dbname=dbnamehere', 'usernamehere', 'passwordhere');
} catch(Exception $e) {
    die('connection_unsuccessful');
}

/* Check if table exists */
$db->exec('CREATE TABLE IF NOT EXISTS subscribers (email VARCHAR(255), time VARCHAR(255))');

/* Check if email has been posted */
if ( isset($_POST['email']) ) {

    /* Validate email */
    if ( isValidEmail($_POST['email']) ) {

        /* Check for duplication */
        $query = $db->prepare('SELECT COUNT(*) AS count FROM subscribers WHERE email = :email');  
        $query->execute(array(':email' => $_POST['email']));
        $result = $query->fetch();

        if ( $result['count'] == 0 ) { // E-mail is unique.

            $query = $db->prepare('INSERT INTO subscribers (email, time) VALUES (:email, :time)');  
            $query->execute(array('email' => $_POST['email'], 'time' => date('Y-m-d H:i:s')));

            /* Send mail notification */
            $to = 'newsubscriber@xyz.com'; // Email notified of the new subscription
            $subject = 'New subscriber';
            $message = 'Hi, you have one new subscriber. This is his/her e-mail address: ' . $_POST['email'] . '.';
            $headers = "From:" . $_POST['email'];
            mail($to,$subject,$message,$headers);

            echo 'successful';

        } else { // E-mail is already being used.
            echo 'already_subscribed';
        }

    } else {
        echo 'invalid_email';
    }

}