$re = '/^(?<name>(?:[a-z0-9]+(?:[-_][a-z0-9]+)*(?<separator>[_\.#\/\\\\*\- ]?))?)(?<!\d)(?<number>\d+)\.(?<extension>[a-z]{3})$/m';
$str = 'tot0_tutu_00001.tif
tot0.0001.tif
tot0#00001.tif
tot0/0001.tif
tot0\\00001.tif
tot0*0001.tif
00001.tif
tot0-tutu_0001.tif
tot0-tutu-00001.tif
tot0-tutu 000001.tif
tot0-tutu000001.tif';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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