help me to change mysql code to php

can anyone help me changing this code to php?

SELECT a1.mark_id, a1.student_id,  
COUNT(a2.quiz) Rank 
FROM mark a1, mark a2 WHERE a1.quiz < a2.mark_quiz
OR (a1.mark_total=a2.quiz AND a1.student_id = a2.student_id) 
GROUP BY a1.student_id, a1.quiz ORDER BY a1.quiz DESC, a1.student_id DESC


thanks.