javascript & php

I have problem with variables in javascript and php. I have code in php and in this code I insert some values from javascript.: $color = "<script><!-- document.write(screen.colorDepth) //--> </script>"; when I write command echo $color - result is correct. but when i need insert or select some values from database with this value ($color) result is not correct this is my code : $query = mysql_query("select id from color where color = '$color' "); $a = mysql_num_rows($query); result is 0. but in my database i have record where is value like value $color. roman