$re = '/^[\w,\s-]+\.(jpg|jpeg|png|gif|pdf)$/m';
$str = 'resource.png
resource.zip
resource.pdf
resource.
resource.jpg
resource.jpeg
.pdf
r$esource.pdf
// You can show origina post on albertcolom.com/blog';
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