Interestingly, setting different target locales results in different, yet appropriate, transliterations. For example:
<?php
//some German
$utf8_sentence = 'Weiß, Goldmann, Göbel, Weiss, Göthe, Goethe und Götz';
//UK
setlocale(LC_ALL, 'en_GB');
//transliterate
$trans_sentence = iconv('UTF-8', 'ASCII//TRANSLIT', $utf8_sentence);
//gives [Weiss, Goldmann, Gobel, Weiss, Gothe, Goethe und Gotz]
//which is our original string flattened into 7-bit ASCII as
//an English speaker would do it (ie. simply remove the umlauts)
echo $trans_sentence . PHP_EOL;
//Germany
setlocale(LC_ALL, 'de_DE');
$trans_sentence = iconv('UTF-8', 'ASCII//TRANSLIT', $utf8_sentence);
//gives [Weiss, Goldmann, Goebel, Weiss, Goethe, Goethe und Goetz]
//which is exactly how a German would transliterate those
//umlauted characters if forced to use 7-bit ASCII!
//(because really ä = ae, ö = oe and ü = ue)
echo $trans_sentence . PHP_EOL;
?>