<?php
$name = 'Schermata07-2456482alle14.34.40.png';
$info = pathinfo($name);
$name = preg_replace("/[^\w-]+/", "", $info['filename']);
// check if we have an extension
if (isset($info['extension'])) {
$name .= '.' . preg_replace('/[^\w]/', '', $info['extension']);
}
echo $name;