<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>Temizle</title>
    </head>
<?
 $page = $_GET["page"];
 if($page == "")
	{
?>
	<body>
    <form id="form1" name="form1" method="post" action="?page=temizle">
    <textarea name="textarea" id="textarea" cols="50" rows="10"></textarea>
        <input type="submit" name="button" id="button" value="Submit" />
    </form>
<?  }
elseif($page == "temizle")
{
	echo $_POST["textarea"]."<br>";
  	echo TRCharEscape($_POST["textarea"],'<B>','</B>');
}
function TRCharEscape($str,$tagopen,$tagclose) { 
	$search = array('Ç','ç','Ğ','ğ','ı','İ','Ö','ö','Ş','ş','Ü','ü'); 
	$replace = array($tagopen.'C'.$tagclose,$tagopen.'c'.$tagclose,$tagopen.'G'.$tagclose,$tagopen.'g'.$tagclose,$tagopen.'i'.$tagclose,$tagopen.'I'.$tagclose,$tagopen.'O'.$tagclose,$tagopen.'o'.$tagclose,$tagopen.'S'.$tagclose,$tagopen.'s'.$tagclose,$tagopen.'U'.$tagclose,$tagopen.'u'.$tagclose); 
	$new_text = str_replace($search,$replace,$str); 
	echo $new_text; 
} 

?>
    </body>
    </html>
Buyur çalışıyor. Burada echo TRCharEscape($_POST["textarea"],'<B>','</B>'); <b> </b> kalın yapmaya yarıyor. İtalik yapmasını istiyorsan eğer <B> </B> yerine <I> </I> yazman yeterlidir. hem kalın hem italik için ise '<b><I>','</I></B> yazman yeterlidir.