正则表达式PHP preg_match_all

Question

I got this code from the WWW:

  private function initialize_loops($template){
        preg_match_all('/{LOOP:([w]+)[^}]*}((s*?.*?)*){\/LOOP:\1}/', $template, $matches, PREG_SET_ORDER);
        foreach ($matches as $match) {
            $template = str_ireplace($match[0], '<!–LOOP('.$match[1].')–>', $template);
            $this->loop_templates[strtoupper($match[1])] = $match[2];
            if(!array_key_exists(strtoupper($match[1]), $this->loops)){
                $this->loops[strtoupper($match[1])] = array();
            }
        }
        return $template;
   }

The Input String is: (for example)

<tbody>
    {LOOP:USERLIST}
    <tr>
      <td>{VAR:ID}</td>
      <td>{VAR:D-NAME}</td>
      <td>{VAR:ROLE}</td>
      <td>{VAR:ACTIONS}</td>
    </tr>
    {/LOOP:USERLIST}
  </tbody>

I don't know for what reasons they created that RegEx in the code, becouse ist not working!

I Tried to get it workin on ReExr.com, so far I have:

/{LOOP:([^}]+)}((s*?.*?)*){\/LOOP:\1}/img

Thats still not working {LOOP:([^}]+)}{\/LOOP:\1} already works for {LOOP:USERLIST}{/LOOP:USERLIST}.

So my Problem is the middle Part: ((s*?.*?)*)

I absoluty cann't see why where is a s in the Expression or how it should work. Hope somebody has a Suggestion how to do it? Or an Explanation of ((s*?.*?)*)?

Answer 1

Probably there's simply a backslash missing:

((\s*?.*?)*)

At a first glance, it seems that they wanted to parse leading whitespaces separately. However, that doesn't explain why the spaces are in the same pattern group as the rest.

Another possibility is that they noticed that . doesn't match newlines. But instead of using the proper pattern modifier "s" (PCRE_DOTALL), they tried to catch the newlines via the \s whitespace pattern.

Either way, just ignore that crap. The following regex should do the trick:

'/{LOOP:([^}]+)}(.*?){\/LOOP:\1}/sg'

By the way, I don't see why you added the "i". Please don't do that. I don't think it is a good design for a template system to match {LoOp:test}...{/loOP:test}.

Also, it doesn't make any sense to add the "m" modifier, since the regex doesn't contain any anchor, neither ^ nor $.