$re = '/\\\\(?:xn|[brw])([\s\S]+?)\r?\n/';
$str = '\\xn[Lan]Allez, il faut se dépécher, RED !
\\xn[Lan]Allez, il faut se dépécher, RED !
\\bI\'ll stay here, then
\\rFirst, you should restore your Pokémon to full health.
\\rFirst, you should restore your Pokémon to full health.
\\w[signskin]Once you save your game, you can access the Mystery Gift.
\\w[signskin]Once you save your game, you can access the Mystery Gift.
';
preg_match_all($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