title: What do the ENT_HTML5, ENT_HTML401, ... modifiers on html_entity_decode do?
body: <p>Since php 5.4 <strong>html_entity_decode</strong> introduces four new flags, with a minimal explanation</p>
  
  <pre><code>ENT_HTML401 Handle code as HTML 4.01.
  ENT_XML1    Handle code as XML 1.
  ENT_XHTML   Handle code as XHTML.
  ENT_HTML5   Handle code as HTML 5. 
  </code></pre>
  
  <p>I want to understand what are they for. In which cases are they significant?    </p>
  
  <p>My guess, (but may I be wrong) is that any different standard, encodes some unusual chars but any other don't, so in order to respect that, they are here.</p>
  
  <p>My research: <strong>htmlentities</strong> has the same minimal explanation, with no examples too.  I have googled with no luck.</p>