title: php regex special character
body: <p>I have:</p>
  
  <pre><code>$regExge = "/(?!((&lt;.*?)))\b(Öffnung)\b(?!(([^&lt;&gt;]*?)&gt;))/s";
  $replacege = "&lt;a href=''&gt;Öffnung&lt;/a&gt;";
  </code></pre>
  
  <p>And I used preg_replace to replace Öffnung string to html <code>&lt;a href=''&gt;Öffnung&lt;/a&gt;</code></p>
  
  <pre><code>$content = preg_replace($regExge, $replacege, $content);
  </code></pre>
  
  <p>But it not working, only working with normal string.</p>
  
  <p>There any way? Thank you.</p>