title: What characters should be replaced to avoid HTML being output?
body: <p>I have some user input in a website, and <strong>I don't want to allow HTML</strong> when outputting that input with PHP later.</p>
  
  <p>I think that the only dangerous characters are <code>&lt;</code>, <code>&gt;</code>, <code>/</code>(slash) and <code>\</code> (backslash).</p>
  
  <p>Am I right?</p>
  
  <p>So, for example, if I replace <code>&lt;</code> with <code>&amp;#60;</code> will it be enough to prevent HTML being output?</p>