Comment changer une chaîne en UTF8 en PHP ?

$str = "123456789";

$str = iconv('ASCII', 'UTF8', $str);

<?php
//some German
$utf8_sentence = &#39;Weiß, Goldmann, Göbel, Weiss, Göthe, Goethe und Götz&#39;;

//UK
setlocale(LC_ALL, &#39;en_GB&#39;);

//transliterate
$trans_sentence = iconv(&#39;UTF-8&#39;, &#39;ASCII//TRANSLIT&#39;, $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, &#39;de_DE&#39;);

$trans_sentence = iconv(&#39;UTF-8&#39;, &#39;ASCII//TRANSLIT&#39;, $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;

?>