title: Php pattern descriptions
body: <p>What does code in PHP, such as</p>
  
  <pre><code>"/(?&lt;!\..|\...|\....)([\?\!\.]+)\s(?!.\.|..\.|...\.)/u"
  </code></pre>
  
  <p>mean? I'm looking for general documentation, not to understand this specific case.</p>
  
  <p>Thank you.</p>