Here is first step, creating form, put it where you want your BUY button to be, it can be on any page, you can create it by buttons wizard on PayPal site, just add this notify_url hidden input.
You can edit those fields with php entering amount, item_name, business email, custom...
<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="business" value="any-email-you-want@domain.com">
<input type="hidden" name="lc" value="US">
<input type="hidden" name="item_name" value="Item Name">
<input type="hidden" name="item_number" value="150">
<input type="hidden" name="amount" value="100.00">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="button_subtype" value="services">
<input type="hidden" name="no_note" value="1">
<input type="hidden" name="no_shipping" value="1">
<input type="hidden" name="tax_rate" value="0.000">
<input type="hidden" name="shipping" value="0.00">
<input type="hidden" name="custom" value="user_id_goes_here">
<input type="hidden" name="bn" value="PP-BuyNowBF:btn_buynowCC_LG.gif:NonHosted">
<input type="hidden" name="notify_url" value="http://checking-url-goes-here/file.php">
<input type="image" src="https://www.sandbox.paypal.com/en_US/i/btn/btn_buynowCC_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_US/i/scr/pixel.gif" width="1" height="1">
</form>
Second step, checking is it valid payment, file.php ( or any file URL you specify in notify_url hidden input in form above ) :
<?php
$req = 'cmd=_notify-validate';
foreach ($_POST as $key => $value) {
$value = urlencode(stripslashes($value));
$req .= "&$key=$value";
}
$header .= "POST /cgi-bin/webscr HTTP/1.0\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
$header .= "Content-Length: " . strlen($req) . "\r\n\r\n";
$fp = fsockopen ('ssl://www.paypal.com', 443, $errno, $errstr, 30);
if (!$fp) {
//ERROR READING PAGE - CODE ERROR
} else {
fputs ($fp, $header . $req);
while (!feof($fp)) {
$res = fgets ($fp, 1024);
if (strcmp ($res, "VERIFIED") == 0) {
//VALID CODE, DO WHATEVER YOU WANT WITH IT HERE, PAYMENT IS CONFIRMED...
}
else if (strcmp ($res, "INVALID") == 0) {
//INVALID CODE
}
}
?>
You can test this code inside:
https://developer.paypal.com/
( PayPal Sandbox )
just replace
www.paypal.com
with
www.sandbox.paypal.com
( you can find it at two places ).
And that's it...
I was asking for this directions, and no one want to direct me here...
I even get -2 rating for this question, but none of those minuses was smart enough to write me those examples, as I ask for...
And I'm the one who deserve minuses?
( I hope someone will find those examples useful )