$re = '/RestApiUsernameToken Username="([^"@]+)", Domain="([^"@]+){0,1}", Digest="([^"]+)", Nonce="([^"]+)", Created="(\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z)"/';
$str = 'RestApiUsernameToken Username="admin", Domain="default", Digest="+PJg7Tb3v98XnL6iJVv+v5hwhYjdzQ2tIWxvJB2cE40=", Nonce="bfb79078ff44c35714af28b7412a702b", Created="2016-04-29T15:48:26Z"';
preg_match($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