The subquery needs an alias name otherwise it won't work. This returns 1 :
SELECT test from -- or fully qualified : aliasname.test
(SELECT 1 as test) aliasname
WHERE test>0
So I presume you require something like :
mysql_query("SELECT something_1, something_2 . . . FROM
(SELECT table1.something_1, table2.something_2 . . .) somealias WHERE . . .");