$re = '/(?s)<span[^>]*>\K.*?.(?=<\/span>)/';
$str = '<span class="st">My Paragraph - you can download free <b>drivers</b> for audio, video, chipset, Wi
Fi or USB, or a <b>driver</b> installation pack for <b>notebook</b>/(for ...</span><br></div>';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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