title: What do these PHP mbstring settings do?
body: <p>I'm trying to figure out exactly what these php.ini settings do. What happens when they're set to different values? When are they necessary? When are they harmful?</p>
  
  <ul>
  <li><a href="http://us3.php.net/manual/en/function.mb-language.php" rel="noreferrer">mbstring.language</a></li>
  <li><a href="http://us3.php.net/manual/en/function.mb-http-input.php" rel="noreferrer">mbstring.http_input</a></li>
  <li><a href="http://us3.php.net/manual/en/function.mb-http-output.php" rel="noreferrer">mbstring.http_output</a></li>
  <li>mbstring.encoding_translation</li>
  </ul>
  
  <p>As usual, the <a href="http://www.php.net/manual/en/mbstring.configuration.php" rel="noreferrer">PHP manual</a> is less than helpful.</p>
  
  <p><strong>EDIT</strong>: Just to clarify, I understand how character encodings work, and I understand how PHP's multi-byte functions differ from their single-byte counterparts. I'm looking for specifics on what the above settings do.</p>
  
  <p><strong>EDIT 2</strong>: OK, it looks like they actually do provide more documentation than just the <a href="http://www.php.net/manual/en/mbstring.configuration.php" rel="noreferrer">page on runtime configuration</a>, which just has one-line summaries. The first three of these have similarly-named functions, and there are more details on the pages that describe the function versions. I added links above.</p>
  
  <p><strong>EDIT 3</strong>: Adding a bounty. I'm looking for specific details on exactly what these settings do, especially the last three. What do they convert from and to, and when do they do it?</p>