ürün adet arttırıldığında iskonto uygulaması başlıyor.
örneğin x ürününden 10 tane seçerseniz 20% hesaplama yapıyor bu sistem.
ve 20% normal fiyattan düşüyor.

<?
include_once("misc/urunfiyati.php");
function valid_email($address)
{
// check an email address is possibly valid
if (ereg('^[a-zA-Z0-9_\.\-]+@[a-zA-Z0-9\-]+\.[a-zA-Z0-9\-\.]+$', $address))
return true;
else
return false;
}
$mesaj="";
if($_POST[CmdSend]){
/*********************************************/
$txturunadedi=$_POST[txturunadedi];
$txtodemesekli=$_POST[txtodemesekli];
$txtkargoadresi=$_POST[txtkargoadresi];
/*********************************************/
$txtad=$_POST[txtad];
$txtsoyad=$_POST[txtsoyad];
$txttelefon=$_POST[txttelefon];
$txteposta=$_POST[txteposta];
$txtmesaj=$_POST[txtmesaj];
/*********************************************/
if($txturunadedi=="" || !is_numeric($txturunadedi) || $txtodemesekli=="" || $txtkargoadresi=="" || $txtad=="" || $txtsoyad=="" || $txttelefon=="" || $txteposta=="" || $txtmesaj=="" || !valid_email($txteposta) ){
if(!valid_email($txteposta)){$mesaj='<font class="sayfaiciyazihata">Lütfen geçerli bir e-posta adresi giriniz!..</font>';}
if($txtmesaj==""){$mesaj='<font class="sayfaiciyazihata">Lütfen mesajýnýzý yazýnýz!..</font>';}
if($txttelefon==""){$mesaj='<font class="sayfaiciyazihata">Lütfen telefon numaranýzý yazýnýz!..</font>';}
if($txteposta==""){$mesaj='<font class="sayfaiciyazihata">Lütfen e-posta adresinizi yazýnýz!..</font>';}
if($txtsoyad==""){$mesaj='<font class="sayfaiciyazihata">Lütfen soyadýnýzý yazýnýz!..</font>';}
if($txtad==""){$mesaj='<font class="sayfaiciyazihata">Lütfen adýnýzý yazýnýz!..</font>';}
if($txtkargoadresi==""){$mesaj='<font class="sayfaiciyazihata">Lütfen sipariþiniz için kargo adresini yazýnýz!..</font>';}
if($txtodemesekli==""){$mesaj='<font class="sayfaiciyazihata">Lütfen sipariþinizin ödeme þeklini belirtiniz!..</font>';}
if(!is_numeric($txturunadedi)){$mesaj='<font class="sayfaiciyazihata">Lütfen ürün adedinizi düzgün giriniz!..</font>';}
if($txturunadedi==""){$mesaj='<font class="sayfaiciyazihata">Lütfen satýn almak istediðiniz miktarý giriniz!..</font>';}
}else{
$kime="info@domainadiniz.com";
$siteurl="http://".$_SERVER["HTTP_HOST"] ;
$konu="$siteurl sitesinden $txturunadedi adet tala sipariþ edildi";
$indirim=(($urunbirimfiyati / 100) * 20) * ($txturunadedi-1);
$toplamfiyat=$urunbirimfiyati * $txturunadedi;
$txttoplamucret=number_format (($toplamfiyat - $indirim),2) + " YTL";
$mesaji='
<table border="0" cellspacing="1" cellpadding="0" width="523">
<tr>
<td width="520" colspan="3">
<b><font face="Tahoma" size="2">Ürün Bilgileri</font></b></td>
</tr>
<tr>
<td width="520" colspan="3">
<hr size="1" color="#E6E6E6"></td>
</tr>
<tr>
<td width="153" height="20">
<font face="Tahoma" size="2">Ürün Adedi</font></td>
<td width="4" height="20">
<font face="Tahoma" size="2">:</font></td>
<td width="363" height="20">
<font face="Tahoma" size="2">'.$txturunadedi.'</font></td>
</tr>
<tr>
<td width="153">
<font face="Tahoma" size="2">Ürün Fiyatý</font></td>
<td width="4">
<font face="Tahoma" size="2">:</font></td>
<td width="363">
<font face="Tahoma" size="2">'.$urunbirimfiyati.' YTL</font></td>
</tr>
<tr>
<td width="153">
<font face="Tahoma" size="2">Toplam Ücret</font></td>
<td width="4">
<font face="Tahoma" size="2">:</font></td>
<td width="363">
<font face="Tahoma" size="2">'.$txttoplamucret.' YTL</font></td>
</tr>
<tr>
<td width="153">
<font face="Tahoma" size="2">Ödeme Þekli</font></td>
<td width="4">
<font face="Tahoma" size="2">:</font></td>
<td width="363">
<font face="Tahoma" size="2">'.$txtodemesekli.'</font></td>
</tr>
<tr>
<td width="153" valign="top">
<font face="Tahoma" size="2">Kargo Adresi</font></td>
<td width="4" valign="top">
<font face="Tahoma" size="2">:</font></td>
<td width="363" valign="top">
<font face="Tahoma" size="2">'.$txtkargoadresi.'</font></td>
</tr>
<tr>
<td width="520" colspan="3">
</td>
</tr>
<tr>
<td width="520" colspan="3">
<b><font face="Tahoma" size="2">Kiþisel Bilgileri</font></b></td>
</tr>
<tr>
<td width="520" colspan="3">
<hr size="1" color="#E6E6E6"></td>
</tr>
<tr>
<td width="153">
<font face="Tahoma" size="2">Adý</font></td>
<td width="4">
<font face="Tahoma" size="2">:</font></td>
<td width="363">
<font face="Tahoma" size="2">'.$txtad.'</font></td>
</tr>
<tr>
<td width="153">
<font face="Tahoma" size="2">Soyadý</font></td>
<td width="4">
<font face="Tahoma" size="2">:</font></td>
<td width="363">
<font face="Tahoma" size="2">'.$txtsoyad.'</font></td>
</tr>
<tr>
<td width="153">
<font face="Tahoma" size="2">Telefon</font></td>
<td width="4">
<font face="Tahoma" size="2">:</font></td>
<td width="363">
<font face="Tahoma" size="2">'.$txttelefon.'</font></td>
</tr>
<tr>
<td width="153">
<font face="Tahoma" size="2">E-Posta</font></td>
<td width="4">
<font face="Tahoma" size="2">:</font></td>
<td width="363">
<font face="Tahoma" size="2">'.$txteposta.'</font></td>
</tr>
<tr>
<td width="153" valign="top">
<font face="Tahoma" size="2">Mesaj</font></td>
<td width="4" valign="top">
<font face="Tahoma" size="2">:</font></td>
<td width="363" valign="top">
<font face="Tahoma" size="2">'.$txtmesaj.'</font></td>
</tr>
<tr>
<td width="520" colspan="3">
</td>
</tr>
<tr>
<td width="520" colspan="3">
<b><font face="Tahoma" size="2">Gönderim Bilgileri</font></b></td>
</tr>
<tr>
<td width="520" colspan="3">
<hr size="1" color="#E6E6E6"></td>
</tr>
<tr>
<td width="153">
<font face="Tahoma" size="2">Gönderdiði Tarih</font></td>
<td width="4">
<font face="Tahoma" size="2">:</font></td>
<td width="363">
<font face="Tahoma" size="2">'.Date("d.m.Y H:i:s").'</font></td>
</tr>
<tr>
<td width="153">
<font face="Tahoma" size="2">IP Adresi</font></td>
<td width="4">
<font face="Tahoma" size="2">:</font></td>
<td width="363">
<font face="Tahoma" size="2">'.$_SERVER[REMOTE_ADDR].'</font></td>
</tr>
</table>
';
$ek="Content-Type: text/html;charset=iso-8859-9\n";
$ek.="From:".$_POST[txteposta];
//echo $mesaji;
if (@mail($kime,$konu,$mesaji,$ek)){
$mesaj='<font class="sayfaiciyazigonderildi">Sipariþiniz baþarýyla alýnmýþtýr.</font>';
}else{
$mesaj='<font class="sayfaiciyazihata">Sipariþiniz hata nedeniyle yollanamamýþtýr.</font>';
}
$txturunadedi="1";$txtodemesekli="";$txtkargoadresi=""; $txtad="";$txtsoyad="";$txttelefon="";$txteposta="";$txtmesaj="";$_POST[CmdSend]="";
}
}
?>
<table width="666" border="0" cellpadding="0" cellspacing="0" class="sayfaiciyazi">
<tr>
<td valign="top"> <br> </td>
<td valign="top" width="396">
<div align="center">
<table border="0" cellspacing="1" cellpadding="0" class="sayfaiciyazi" width="386">
<form action="<?=$_SERVER[REQUEST_URI];?>" name="FrmSiparis" method="POST">
<tr>
<td height="25" colspan="3" style="font-weight: bold"><?=$mesaj;?></td>
</tr>
<tr>
<td width="382" height="21" colspan="3"><b>
Ürün Sipariþ Bilgileri</b></td>
</tr>
<tr>
<td width="382" height="21" colspan="3"><hr size="1" id="cizgi"></td>
</tr>
<tr>
<td width="85" height="21">Ürün Adedi</td>
<td width="4" height="21">:</td>
<td width="293" height="21">
<input type="text" name="txturunadedi" size="3" value="<?if($txturunadedi==''){echo '1';}else{ echo $txturunadedi;}?>" id="inputkutu" onchange="hesapla(<?=$urunbirimfiyati;?>)" onblur="hesapla(<?=$urunbirimfiyati;?>)"></td>
</tr>
<tr>
<td width="85" height="21">Ürün Fiyatý</td>
<td width="4" height="21">:</td>
<td width="293" height="21">
<?=$urunbirimfiyati;?> YTL</td>
</tr>
<tr>
<td width="85" height="21">Toplam Ücret</td>
<td width="4" height="21">:</td>
<td width="293" height="21"><div id="toplamfiyat"></div>
</td>
</tr>
<tr>
<td width="85">Ödeme Þekli</td>
<td width="4">:</td>
<td width="293">
<select name="txtodemesekli" id="textareakutu" size="1">
<option value="" <?if($txtodemesekli==""){echo "selected";}?> >Lütfen Seçiniz</option>
<option value="Kredi Kartý" <?if($txtodemesekli=="Kredi Kartý"){echo "selected";}?> >Kredi Kartý</option>
<option value="EFT/Havale" <?if($txtodemesekli=="EFT/Havale"){echo "selected";}?> >EFT/Havale</option>
<option value="Kapýda Ödeme" <?if($txtodemesekli=="Kapýda Ödeme"){echo "selected";}?> >Kapýda Ödeme</option>
</select></td>
</tr>
<tr>
<td width="85" valign="top">Kargo Adresiniz</td>
<td valign="top" width="4">:</td>
<td width="293">
<textarea name="txtkargoadresi" rows="6" cols="36" id="textareakutu" style="width: 290; height:55"><?=$txtkargoadresi;?></textarea></td>
</tr>
<tr>
<td width="382" colspan="3" height="21"><b>Kiþisel
Bilgileriniz</b></td>
</tr>
<tr>
<td width="382" colspan="3"><hr size="1" id="cizgi"></td>
</tr>
<tr>
<td width="85">Ad</td>
<td width="4">:</td>
<td width="293">
<input type="text" name="txtad" size="20" value="<?=$txtad;?>" id="inputkutu"></td>
</tr>
<tr>
<td width="85">Soyad</td>
<td width="4">:</td>
<td width="293">
<input type="text" name="txtsoyad" size="20" value="<?=$txtsoyad;?>" id="inputkutu"></td>
</tr>
<tr>
<td width="85">Telefon</td>
<td width="4"> </td>
<td width="293">
<input type="text" name="txttelefon" size="20" value="<?=$txttelefon;?>" id="inputkutu"></td>
</tr>
<tr>
<td width="85">E-Posta</td>
<td width="4">:</td>
<td width="293">
<input type="text" name="txteposta" size="20" value="<?=$txteposta;?>" id="inputkutu"></td>
</tr>
<tr>
<td width="85" rowspan="2" valign="top">Mesajýnýz</td>
<td rowspan="2" valign="top" width="4">:</td>
<td width="293">
<textarea name="txtmesaj" rows="6" cols="36" id="textareakutu" style="width: 290; height:55"><?=$txtmesaj;?></textarea></td>
</tr>
<tr>
<td width="293">
<input type="submit" value="Sipariþ Ver" name="CmdSend" id="button">
<input type="reset" value="Temizle" name="CmdClear" id="button"></td>
</tr>
<tr>
<td id="dipnot" height="25"> </td>
<td id="dipnot" height="25" width="4"> </td>
<td id="dipnot" height="25"><b>Not: </b>Bütün alanlar
zorunludur. Lütfen eksiksiz doldurunuz.</td>
</tr>
<tr>
<td valign="top" colspan="3" id="dipnot"> </td>
</tr>
</form>
</table></div>
</td>
</tr>
</table>
<script language="javascript">
<!--
hesapla(<?=$urunbirimfiyati;?>);
//-->
</script>