convert arabic chars to persian
<p>i want to convert arabic chars such as <code>ك</code> and <code>ي</code> to persian .
this code not working :</p>

<pre><code>&lt;?php
$buff='سلامی به گرمي آشنایی';
$buff = str_replace("ی","ي",$buff);
$buff = str_replace("ک","ك",$buff);
?&gt;
</code></pre>

<p>in this code <code>گرمي</code> must be <code>گرمی</code>.</p>
