PHP

I had no idea I had a course in PHP this semester, evidently I do and the exam is tomorrow. I need to learn PHP in 18 hours and complete an assignment before the test. Teach me PHP!

<?php
    function fibs($n) {
        int accum = 1;
        for($i = 1; $i <=n; $i++) accum *= $i;
        return $accum;
    }