title: detecting duplicate string in a explode function php
body: <p>how do i detect duplicate string inside explode?</p>
  
  <pre><code>$str = 'a, b, c, a, a, a, b, e, w, r, d, o'; // example str
  $explode = explode(',', $str);
  </code></pre>
  
  <p>any idea? </p>