$re = '/(?:v_)?([a-zA-Z]+|av)\d?_([a-zA-Z]+)_(?:[a-zA-Z]+(?:_[a-zA-Z]+)*)__(?:int|ext)\d{2}_([a-zA-Z]+(?:_[a-zA-Z]+)*)_\d{2}.*\.ent/m';
$str = 'v_sport2_mizutani_shion__ext01_body_01.ent';
preg_match_all($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