title: Detect non-empty string with regexp?
body: <p>How do I write a PHP regexp which detects that a string is not empty?</p>
  
  <p>Empty means, in this case 0 characters. A single space, or a single newline counts as not empty, for instance.</p>
  
  <p>(It has to be regexp suitable for preg_match(), since I have a lookup table with various regexps and don't want to handle this case in any special way, it would complicate the code to not use a regexp here.)</p>
  
  <p><em><strong>Update:</em></strong></p>
  
  <p>I also can not use any regex modifiers such as "s" outside the <code>//</code> for sad reasons.</p>
  
  <p><em><sup>To downvoters: Is the question too simple? Or not clear enough?</sup></em></p>