paypal in php

<script>
function validate(){
var obj=document.frmPayPal;
//alert("Design");
//var obj=valobj.frmPayPal;

if(obj.amount.value==""){
alert("Please Enter Amount!");
obj.amount.focus();
return false;
}else if(isNaN(obj.amount.value)){
alert("Enter Number Only!");
obj.amount.focus();
return false();
}else if(obj.currency_code.value==""){
alert("Please Select Currency!");
obj.currency_code.focus();
return false;
}else{
return true;
}
}
</script>





<!-- <form id="frmPayPal" name="frmPayPal" action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post" onsubmit="return validate(this)"> -->


                <form id="frmPayPal" name="frmPayPal" action="https://www.paypal.com/cgi-bin/webscr" method="post" onsubmit="return validate(this)" >

<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="business" value="sumanprabhha80@gmail.com">
<input type="hidden" name="item_name" value="Pay for Us">
<input type="hidden" name="item_number" value="1">
  <!-- <input type="hidden" name="amount" value="500"> -->
Amount : <input type="text" name="amount" value="">
</br>
<input type="hidden" name="no_shipping" value="0">
<input type="hidden" name="no_note" value="1">

  <!-- <input type="hidden" name="currency_code" value="EUR">  -->
Currency : <select name="currency_code">
<option value="USD">U.S. Dollars</option>
<option value="EUR">Euros</option>
<option value="AUD">Australian Dollars</option>
</select>
<input type="hidden" name="lc" value="AU">
<input type="hidden" name="bn" value="PP-BuyNowBF">
<input type="hidden" name="return" value="">
<input type="hidden" name="notify_url" value="">
<!-- <input type="hidden" name="cancel_return" value="<?php //$cencelRetUrl?>"> -->
</br>
<button type="submit">Submit</button>
 <!--  <input type="image" src="https://www.paypal.com/en_AU/i/btn/btn_buynow_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online.">
<img alt="" border="0" src="https://www.paypal.com/en_AU/i/scr/pixel.gif" width="1" height="1">-->
</form>