mysql_real_escape_string with PDO PHP

您好，我是PDO的新手，所以感到困惑并;)错误与mysql_real_escape_string..

任何人都可以帮忙，这是我的代码

if(!empty($_POST) && isset($_POST)) { 
include ('connection_pdo.php');
$dbh = new PDO("mysql:host=$host;dbname=$dbname", $user, $pass);
$source_url= mysql_real_escape_string($_POST['source_url']);
$class     = mysql_real_escape_string($_POST['class']);
$year      = mysql_real_escape_string($_POST['year']);
$date      = time();
$ip        = $_SERVER['REMOTE_ADDR'];
$insert = $dbh->prepare("
  INSERT IGNORE INTO school_students_images
            ( folder_name,  image_url,  source_url,  class, year , date , ip )
    VALUES  (:folder_name, :image_url, :source_url, :class, :year, :date, :ip)
");
$a=0;
while ($a<1000){
$a++;
$insert->execute(array(
            'folder_name'=> $name->content, //** geting from other source
            'image_url'  => $link[$a], //** geting from other source
            'source_url' => $source_url,
            'class'      => $class ,
            'year'       => $year ,
            'date'       => $date,
            'ip'         => $ip
            ));
}

它不起作用，但如果我使用它没有

    $source_url= ($_POST['source_url']);
    $class     = ($_POST['class']);
    $year      = ($_POST['year']);
    $date      = time();
    $ip        = $_SERVER['REMOTE_ADDR'];

它正在工作...所以我很困惑在不mysql_real_escape_string数据库的情况下开机自检是否安全？（PDO是否默认提供任何安全性？或者我在这方面做错了...请帮忙