$re = '/kod:[ ]([a-zA-Z]*)[ ]/';
$str = 'sf sdf sdf kod: ahoj sdfsdfsf
kod:
kod: ahoj aaa
kod: ahoj
ahoj kod:';
preg_match_all($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