Values from PHP variables to MYSQL procedure

Hi all at Daniweb,

I'm quite new to PHP and I'm banging my head over this...

query 1 WORKS:

$query = "CALL procedure_is_a_great_way_to_let_db_do_some_work('1','6')";
//both 1 and 6 are IN parameters!

query 2 DOESN'T WORK:
$id_pictures = 1;
$id_names = 6;
$query = "CALL procedure_is_a_great_way_to_let_db_do_some_work('".$id_pictures."','".$id_names."')";
//both 1 and 6 are IN parameters!