您应该使用如下的PayPal Button API：
$sendPayData = array( "METHOD" => "BMCreateButton", "VERSION" => "65.2", "USER" => "username", "PWD" => "password", "SIGNATURE" => "abcdefg", "BUTTONCODE" => "ENCRYPTED", "BUTTONTYPE" => "BUYNOW", "BUTTONSUBTYPE" => "SERVICES", "BUTTONCOUNTRY" => "GB", "BUTTONIMAGE" => "reg", "BUYNOWTEXT" => "BUYNOW", "L_BUTTONVAR1" => "item_number=$invoiceNumber", "L_BUTTONVAR2" => "item_name=$invoiceType", "L_BUTTONVAR3" => "amount=$invoiceTotal", "L_BUTTONVAR4" => "currency_pre=GBP", "L_BUTTONVAR5" => "no_shipping=1", "L_BUTTONVAR6" => "no_note=1", "L_BUTTONVAR7" => "notify_url=http://www.abc.co.uk/paypal/ipn.php", "L_BUTTONVAR8" => "cancel_return=http://www.abc.co.uk/paypal/thanks", "L_BUTTONVAR9" => "return=http://www.abc.co.uk/paypal/return.php");
然后，您可以使用cURL将其发送到他们的API
$curl = curl_init();curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);curl_setopt($curl, CURLOPT_URL, 'https://api-3t.paypal.com/nvp?'.http_build_query($sendPayData));$nvpPayReturn = curl_exec($curl);curl_close($curl);
然后生成无法编辑的加密HTML按钮
<form action="https://www.paypal.com/cgi-bin/webscr" method="post"> <input type="hidden" name="cmd" value="_s-xclick"> <input type="hidden" name="encrypted" value="-----BEGIN PKCS7-----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-----END PKCS7-----"><input type="image" src="https://www.paypal.com/en_US/i/btn/btn_paynow_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_GB/i/scr/pixel.gif" width="1" height="1">
