$re = '/\bMac\b.*\bExchangeWebServices\b/';
$str = 'This expression can only match a string containing Mac and ExchangeWebServices but not just Mac.
This expression should not match Macintosh and ExchangeWebServices!
Mac OS X/10.11.5 (15F34); ExchangeWebServices/6.0 (243);
Mac iOS/10.11.5; ExchangeWebServices/6.0 (243);
Mac OS X/10.5; ExchangeWebServices/6.0 (243);';
preg_match_all($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