$re = '/^(?<fileName>[^.]+\.(?:jpg|png|gif|pdf|xlx))(?:\|(?:width=(?<width>.*?))?,?(?:height=(?<height>.*?))?)?$/m';
$str = 'img2.png|width=83.33333333333334%
robot (f05f0216-caf4-4543-a630-99c2477849d5).png|width=400,height=400
abc.pdf|width=200
dfe.xlx
dfe.gif|height=400
';
preg_match_all($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