- setlocale: documentation ( source)
<?php
$utf8_sentence = 'Weiß, Goldmann, Göbel, Weiss, Göthe, Goethe und Götz';
setlocale(LC_ALL, 'en_GB');
echo iconv('UTF-8', 'ASCII//TRANSLIT', $utf8_sentence) ."\n";
setlocale(LC_ALL, 'de_DE');
echo iconv('UTF-8', 'ASCII//TRANSLIT', $utf8_sentence) ."\n";