$re = '/(?<sup_all>
(?:
(?<!\\\\)\^
(?<sup_text>
(?>\\\\[\^[:blank:]\h]|[^\^[:blank:]\h\v])*+
)
(?<!\\\\)\^
)
|
(?: # or the Microsoft way. Beurk
\<sup\>
(?<sup_text>
((?!\v).)+
)
\<\/sup\>
)
)/Jx';
$str = '2^10^ is 1024.
Space is not allowed:
P^a cat^
But it\'s ok if it is escaped
P^a\\ cat^
Line break is a no-no, even escaped
P^a\\
cat^
Hmm <sup>This is a Microsoft superscript!</sup>
H^2^0
text^a\\ superscript^
';
preg_match_all($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