php real_escape_string(), query not working anymore

Question

I want to be able to add and update certain information. Now it was all working fine untill I found out the script no longer works when there's quotation marks in the text being sent to the database.

So I've done some research and found out I had to use the mysql_real_escape_string() function to ignore the quotation marks. I've done this but the script now isn't working at all anymore. I think the problem lies in the query part but i don't see the problem. Below is the code:

<?php
if(isset($_POST['bevestiging']))
{   
    $ID = (int)$_GET['ID'];

    $titel = mysql_real_escape_string($_POST['Titel']);
    $ondertitel = mysql_real_escape_string($_POST['ondertitel']);
    $wanneer = mysql_real_escape_string($_POST['wanneer']);
    $datum = mysql_real_escape_string($_POST['datum']);
    $afbeelding = mysql_real_escape_string($_POST['afbeelding']);
    $intro = mysql_real_escape_string($_POST['intro']);
    $main = mysql_real_escape_string($_POST['main']);

    $query = "UPDATE voorstellingen 
              SET '$titel','$ondertitel','$wanneer','$datum','$afbeelding','$intro','$main' 
              WHERE id = $ID";

    mysql_query($query) or die('Error, bewerken van voorstelling is mislukt');  
    $query ="FLUSH PRIVILEGES"; 
    echo"De voorstelling is succesvol bewerkt";
}
else{

    $ID = (int)$_GET['ID'];
    $query="SELECT * FROM voorstellingen WHERE id = $ID";
    $result = mysql_query($query) or die('Error, bewerken van voorstelling is     mislukt');;
?>

Answer 1

your update query should be like:

$query = "UPDATE voorstellingen SET title = '".$titel."' .....";

See: UPDATE Syntax