HELP TO VALIDATE CHECKBOXES

Hi! I'm having some problems with checkboxes at the moment, and i'd be glad if you could help me solve it... i'll give a brief explanation of the situation first so that you can understand what i'm talking about :-) I have the tables 'User' (containing userid,etc), 'Category' (containing category_id) and the table User_Category (user)id and category_id) since i have a many-to-many relationship between user and category Now, when i add a new user, i display a list of the category names, with a checkbox next to each, so that the user can check more than 1 category Now, the problem: let's say i want to modify a particular user.... i thus have a link on the user, e.g. <a href="modify.php?id='.$row["user_id"].'">'.$row["name"].'</a> Now, on modify.php, i want to display all the values that the user posted initially (lastname, firstname, username, password, etc...) Here i also want to display all the category names with a checkbox next to each (this is easy!) $sql = "SELECT * FROM category"; $result = mysql_query($sql); // (this is referenced as LOOP1 below) while ($row = mysql_fetch_array($result)) { echo $row["name"]; echo '<input type="checkbox" name="cat[]" value='.$row["category_id"].'>'; } Now, to get the values of category_id that the user previously selected, i just need to do $qry = "SELECT category_id FROM user_category WHERE user_id='$id'"; $result2 = mysql_query($qry); // for example, i have 8 records in my table category, therefore i'll have 8 checkboxes with id values 1, 2...8 // now assume that, when filling his form, the user clicked the checkboxes with id values 1, 2, 3, 4, 5 only NOW ==>>> THE PROBLEM: (finally we reach there!!!) :-) HOW do i modify LOOP1 so that i loop the second query $qry to validate which value of category_id in each checkbox corresponds to the values returned by my query $qry, and i check ONLY THOSE checkboxes, and leave the other checkboxes as unchecked? I'd be grateful if you could help Thanks and regards, Yog.