<?php

function nthstrpos($haystack, $needle, $nth) {
	$count = 0;
	$pos = -1;
	do {
		$pos = strpos($haystack, $needle, $pos + 1);
		$count++;
	} while ($pos !== false && $count < $nth);
	return $pos;
}

// your code goes here
var_dump(nthstrpos('banana', 'a', 1));
var_dump(nthstrpos('banana', 'a', 2));
var_dump(nthstrpos('banana', 'a', 3));
var_dump(nthstrpos('banana', 'a', 4));
var_dump(nthstrpos('banana', 'n', 1));
var_dump(nthstrpos('banana', 'n', 2));
var_dump(nthstrpos('banana', 'n', 3));