title: utf8 string length
body: <p><code>strlen()</code> function in php could not return correctly string lenght of utf8 chars,  for example <code>سلام</code> is 4 char but after using strlen thats return 8 chr</p>
  
  <pre><code>&lt;?php
  echo strlen('سلام');
  ?&gt;
  </code></pre>