$re = '/href=".*?([\w-]+\.pdf)"/m';
$str = '<a class="btn btn-small pad-button" href="/Tests/English/english_2011_summer_A-Q_b.pdf">eng1</a><br>
<a href="english_2011_summer_A-Q_c.pdf">eng2</a>
';
preg_match_all($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