title: How to determine if a string is a valid v4 UUID?
body: <p>I'm making a validator based on <a href="http://en.wikipedia.org/wiki/Universally_unique_identifier" rel="nofollow noreferrer">UUID</a> generated by client browser, I use this to identify a certain type data that the user sends; and would like to validate that the <code>UUID</code> that client sends it is in fact a valid <a href="http://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_.28random.29" rel="nofollow noreferrer">Version 4</a> <code>UUID</code>.</p>
  <p>I found this <a href="https://stackoverflow.com/questions/6223185/php-preg-match-uuid-v4">PHP preg_match UUID v4</a>, it's close  but not exactly what I'm looking for. I wish to know if exists something similar to <code>is_empty()</code> or <code>strtodate()</code> Where if string is not valid Sends <code>FALSE</code>.</p>
  <p>I could do based on the regular expression but I would like something more native to test it.</p>
  <p>Any ideas?</p>