$re = '/^.*\?comeFrom\=([^&]+)&jobId\=([0-9]+)&distance\=([0-9]+).*$/';
$str = '/visitor/browseJobDetails.do?comeFrom=email&jobId=3931052&distance=18&rx=email_NJNY%7CProvider_Featured%7Cjobtitle%7C91942%7CCHILDCARE';
$subst = "$2";
$result = preg_replace($re, $subst, $str, 1);
echo "The result of the substitution is ".$result;
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