$re = '/[^\d\p{L}.,\s]+/u';
$str = 'L\'élève s\'est cassé la figure!
Il faut appeler le numéro 118 en cas d\'accident.
#drop-some-chars';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php