$re = '/.*(?<=email&jobId\=)(\d+)(?=&distance).*/';
$str = '/visitor/browseJobDetails.do?comeFrom=email&jobId=3931052&distance=18&rx=email_NJNY%7CProvider_Featured%7Cjobtitle%7C91942%7CCHILDCARE`';
preg_match($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