The code posted above by Joerg Krause only works for a string which ends with one of the delimiters. A possible fix is:
<?php
$text = "What?No delimiters,shit happens here.this solves all problems.";
preg_match_all("/(\w+[,. ?])+/U", $text, $words);
preg_match("/(\w+)$/", $text, $lastword);
$words[0][] = $lastword;
foreach($words[0] as $part) $uwords[] = ucfirst($part);
$text = implode("", $uwords);
echo $text;
?>