$re = '/^ALL(?::[!-]?[ak]?[A-Z0-9]+(?:[+-]?[ak]?[A-Z0-9]+)*)*(?:,ALL(?::[!-]?[ak]?[A-Z0-9]+(?:[+-]?[ak]?[A-Z0-9]+)*)*)*$/m';
$str = 'ALL:!kRSA:!CBC,ALL:-aRSA:-CBC:SHA256,ALL:!kRSA,ALL:!aRSA,ALL:!RSA,ALL:!EDH-RSA-DES-CBC-SHA,ALL:!DES-CBC,ALL:!DES,ALL:-RSA+AES-128-CBC+SHA256
invalid
ALL:+DES,+DES,-DES,DEFAULT:-aRSA,akRSA,kDHE-aRSA,!ECDHE';
preg_match_all($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