PHP致命错误：找不到类'PDO'

Question

登录时出现问题＆amp; error_log在connecion.php文件中显示 PHP致命错误：未找到类'PDO'。
php connection.php代码：

<? php
$dsn = 'mysql:host=localhost;dbname=bot_db';
$username = 'bot_db';
$password = '**********';
try {
    $con = new PDO($dsn, $username, $password);
} catch (PDOException $e) {
    $error_message = $e->getMessage();
    include('../errors/err.php');
    exit();
}  
?>

在

中显示致命错误

$con = new PDO($dsn, $username, $password);