Integration of PayPal standard payment implementation in PHP

One customer needs to integrate the PayPal payment feature on the website two days ago. after checking the information, a simple record is as follows: the PayPal payment feature has been updating documents and interfaces, here is a simple payment process as follows:

1. on the checkout page of the website, set a form submitted to the PayPal website, which contains the amount, product name, Merchant's collection account, and URL returned after successful checkout,

2. you can click the 'use PayPal checkout 'button to go to the PayPal checkout page, enter your PayPal username and password, and confirm the payment.

3. PayPal determines which page of the website is returned based on whether the payment is successful, and initiates a post request to a page of the website in the background. this action is called IPN, tell the website the receipt of the payment. for example, completed indicates that the payment is complete.

4. The website can deliver the goods or other processing logic to the user after receiving the Alipay notification from PayPal.

Here is an illustration.

Simpler flowchart

To complete the entire process, we only need two pages for processing.

1. The checkout. php page is used to display information about the shopping cart and allows users to click the button to navigate to PayPal for payment.
2. Notify. php this page is used to receive the IPN information of PayPal, determine whether the user's payment status is received, and process the business logic after the website receives the payment

Record the code:
The checkout. php page can actually be HTML

The code is as follows:

This form contains some items that must be added for PayPal payment. it should be noted that notify. php is the callback y that PayPal will call in the background. the php page has two functions. one is to receive post content from PayPal and add a tag to return the content. The other is to receive authentication information from PayPal and perform internal logic processing on the website.

The code is as follows:

$ Req = 'cmd = _ policy-validate ';
Foreach ($ _ POST as $ key => $ value ){
$ Value = urlencode (stripslashes ($ value ));
$ Req. = "& $ key = $ value ";
}
// Post back to PayPal system to validate
$ 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 ";
$ Fp = fsockopen ('SSL: // www.paypal.com ', 443, $ errno, $ errstr, 30 );
If (! $ Fp ){
// HTTP ERROR
} Else {// HTTP OK
Fputs ($ fp, $ header. $ req );
While (! Feof ($ fp )){
$ Res = fgets ($ fp, 1024 );
If (strcmp ($ res, "VERIFIED") = 0 ){
// Process business of website
}
Else if (strcmp ($ res, "INVALID") = 0 ){
// Log for manual investigation
}
}
Fclose ($ fp );
}