Windows uses the local character encoding (cp125*) for file and directory name.

localEncoding.php

<?php
function utf8ToLocalEncoding($s) {
	if (substr(PHP_OS, 0, 3) === 'WIN') {
		$tmp = explode(".", setlocale(LC_CTYPE, 0));
		if (isset($tmp[1]) && is_numeric($tmp[1]))
			$s = @iconv("UTF-8", "cp" . $tmp[1] . "//TRANSLIT", $s);
	}
	return $s;
}

function localEncodingToUtf8($s) {
	if (substr(PHP_OS, 0, 3) === 'WIN') {
		$tmp = explode(".", setlocale(LC_CTYPE, 0));
		if (isset($tmp[1]) && is_numeric($tmp[1]))
			$s = @iconv("cp" . $tmp[1] . "//TRANSLIT", "UTF-8", $s);
	}
	return $s;
}

$original = "ěščřžýáíé";
$a = utf8toLocalEncoding($original);
$b = localEncodingToUtf8($a);

var_dump($original, $a, $b, $original === $b);