Building a query string

This list has helped me out alot and I hope it can do it one more time. I need to build a MySQL query based on 11 different options from a form. Some options will have values others will be checkboxes to say include in the query. How I thought about going at it was using a default query string and add additional strings to the default string based on results of the form. $query_str = "SELECT * FROM listings WHERE id > 0 "; if ($garage != "") { $garage_str = "AND garage = '$garage' "; //add $garage_str to $query_str// } This would continue through all eleven options then produce a query string with all included query options needed. Can this be done this way? If so, how do I add a string to a string? Thanks, Ed