Simple regex not

Question

I'm looking for a way to write the following in only one preg_replace

$url = "stackoverflow";
  if(!preg_match('/apple/',$url)){
    $url = $url.".apple.com";
  }

Answer 1

$str = 'something';
echo preg_replace('/^(?:(?!apple).)*$/is', '$0.apple.com', $str);

ps: modifiers is might be useful.

(?: )* makes non-capturing pattern. It matches zero or more instances of a (?!apple) . Which is anything except of apple and $0 tells to take the whole string when pattern is matched. Example suggested above is not the same, because it will match anything when the string does not start with apple as ?!apple condition is applied only once, at the beginning of the string.