title: regex, negative lookahead (?!?) find < tags not followed by?
body: <p>How to find <code>&lt;</code> tags not followed by <code>?</code></p>
  
  <pre><code>$htmlStr = " ba &lt;div&gt;b &lt;? &lt;/div&gt;n";
  $regex1 = '#&lt;#'; // finds 3 '&lt;' 
  $regex2 = '#&lt;(?!?)#'; // does not find anyhting, although should find two '&lt;' not followed by '?' 
  </code></pre>