$re = '/.*zz\s*:\s*(.*)[\n\r]/';
$str = '{
xx :
yy :
zz : sample 123123
}
HTTP/1.1 202... blah blah blah
Content-Length: 35
X-Frame-Options: deny
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Connection: close';
preg_match($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