title: php regex unknown whitespace
body: <p>I am having a hard time figuring out what is happening with this regexp to match multiple whitespace :</p>
  
  <pre><code>$str = '   ';
  
  if (preg_match_all('/\s{2,}/', $str, $matches)) {
      var_dump($matches);
  }
  </code></pre>
  
  <p>The fact is, if i replace str value with 3 "real" spaces, it works as expected, but obviously the characters in str are not whitespaces (copy paste from other source) !! But i need to match them to replace them with real spaces/whatever.</p>
  
  <p>My question: What are those simple space looking characters in str and more important, how do i target them in a regexp ?</p>