What are the potential risks of relying on GET data from PayPal for transaction verification in PHP scripts?

Relying solely on GET data from PayPal for transaction verification in PHP scripts can pose security risks as the data can be manipulated or spoofed by malicious users. To mitigate this risk, it is recommended to use PayPal IPN (Instant Payment Notification) for transaction verification, as it provides a secure and reliable way to confirm payment details. 

// Sample PHP code snippet using PayPal IPN for transaction verification

// Step 1: Validate IPN request
$req = 'cmd=_notify-validate';
foreach ($_POST as $key => $value) {
    $value = urlencode(stripslashes($value));
    $req .= "&$key=$value";
}

$ch = curl_init('https://www.sandbox.paypal.com/cgi-bin/webscr');
curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $req);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Connection: Close'));

$res = curl_exec($ch);
curl_close($ch);

// Step 2: Process IPN response
if ($res == 'VERIFIED') {
    // Payment verified, process the transaction
    // Insert your transaction processing logic here
} else {
    // Payment verification failed, handle the error
    // Log the error or take appropriate action
}

Keywords

GET data PayPal transaction verification risks PHP scripts

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