$re = '/^("+)((.*?)(?<!\\\\)(?:\\\\\\\\)*)\1$/m';
$str = '"""hello world"""""
""hello\\""world""
"hello\\"world"
"hello world\\\\"
"\\"hello world\\""
"hello world\\\\\\"';
preg_match_all($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