<?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));
 

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