$re = '/#Ограничитель 1
((\<)|(\()|(\[)|(\{)|
((?=[[:ascii:]])[^\s\w\\\\\)\]\}\>]))
#Шаблон
((?#ignore comments like this in the regular expression)
(?(6)
(?(?=(?:(?!\6).|(?<=\\\\)\6)*[^\\\\][\(][\?][\#])
(?:(?!\6).|(?<=\\\\)\6)*[^\\\\][\(][\?][\#]
[^\)]*(?-1)))
.*?)
#Ограничитель 2
#экранированные обратные слеши +
#неэкранированный ограничитель
(?(2)(?<!(?<!(?<!(?<!(?<!(?<!(?<!(?<!\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\>)
(?(3)(?<!(?<!(?<!(?<!(?<!(?<!(?<!(?<!\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\))
(?(4)(?<!(?<!(?<!(?<!(?<!(?<!(?<!(?<!\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\])
(?(5)(?<!(?<!(?<!(?<!(?<!(?<!(?<!(?<!\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\})
(?(6)(?<!(?<!(?<!(?<!(?<!(?<!(?<!(?<!\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\\\\)\6)
#Модификаторы шаблонов
#PHP [mixXsuUAJ] JavaScript [gmi] python [gmixsu]
((?(6)(?:[mixXsuUAJ]*)|(?(?=.*?[mixXsuUAJ]+)[mixXsuUAJ]+)))/xs';
$str = 'test $asdf\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\$\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\$iU';
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