$re = '/\[(.+)?\] (.+?) (S\d* )?- (\d+) \[(.+)\]/i';
$str = '[HorribleSubs] Fate Kaleid Liner PRISMA ILYA - 01 [720p]
[HorribleSubs] Akame ga Kill! - 02 [720p].mkv
[HorribleSubs] Aldnoah Zero - 08 [720p]
[HorribleSubs] Deadman Wonderland - 02 [720p]
[HorribleSubs] Tokyo Ghoul Root A - 01 [720p]
[HorribleSubs] Sword Art Online II - 02 [1080p]
[HorribleSubs] Yahari Ore no Seishun Love Come wa Machigatteiru Zoku - 07 [720p].mkv
[HorribleSubs] Love Live! S2 - 02 [720p]
[HorribleSubs] Fairy Tail S2 - 02 [720p].mkv';
preg_match_all($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