$re = '%Content-ID: <http://tempuri\.org/1/636644204289948690>([\s\S]*?)--uuid%';
$str = 'Content-ID: <http://tempuri.org/1/636644204289948690>
Content-Transfer-Encoding: binary
Content-Type: application/octet-stream
%PDF-1.4
%���� (lots of binary content here)
--uuid:7329cfb8-46a4-40a8-b15b-39b7b0988b57+id=4--';
preg_match_all($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