- substr: documentation ( source)
- stristr: documentation ( source)
- str_replace: documentation ( source)
<?php
$s = "Römer";
$rest = "Römer";
$result = "Römer";
do {
$rest = stristr($rest,$s);
$replace = substr($rest,0,strlen($s));
$result = str_replace($replace,"<span class='textHighlight'>{$replace}</span>",$result);
$rest = substr($rest,strlen($s));
} while ($rest !== false);
echo $result;