$username = str_replace(" ","-",$username);
	    $username = str_replace("'","_",$username);
	    $username = str_replace("ä","a",$username);
	    $username = str_replace("ö","o",$username);
	    $username = str_replace("ü","y",$username);
          $username = str_replace(":","_",$username);
          $username = str_replace("ğ","g",$username);
          $username = str_replace("Ğ","G",$username);
          $username = str_replace("ş","s",$username);
          $username = str_replace("Ş","S",$username);
          $username = str_replace("ç","c",$username);
          $username = str_replace("Ç","C",$username);
          $username = str_replace("!","",$username);
          $username = str_replace("&","",$username);
          $username = str_replace("ı","i",$username);

functions.php de bunları tamamla.bende aynı sorun vardı.yavaş yavaş bütün türkçe karakterleri editliyip forumda vericem