Verifying In-App Purchase Receipts

In-app purchase validation is crucial for ensuring that users have made legitimate purchases and granting them access to premium content or functionality. Despite the availability of documentation, it can be challenging to implement effective receipt validation.

One approach involves sending the receipt data to a PHP server, which then forwards it to the Apple App Store for verification. A successful response confirms the validity of the purchase, allowing you to proceed with recording the transaction on your server.

However, if you encounter "invalid status" responses during receipt validation, it's essential to check for any typos in your code. The following sample code provides a solution:

- (BOOL)verifyReceipt:(SKPaymentTransaction *)transaction {
    NSString *jsonObjectString = [self encode:(uint8_t *)transaction.transactionReceipt.bytes length:transaction.transactionReceipt.length];      
    NSString *completeString = [NSString stringWithFormat:@"http://url-for-your-php?receipt=%@", jsonObjectString];               
    NSURL *urlForValidation = [NSURL URLWithString:completeString];       
    NSMutableURLRequest *validationRequest = [[NSMutableURLRequest alloc] initWithURL:urlForValidation];              
    [validationRequest setHTTPMethod:@"GET"];         
    NSData *responseData = [NSURLConnection sendSynchronousRequest:validationRequest returningResponse:nil error:nil];  
    [validationRequest release];
    NSString *responseString = [[NSString alloc] initWithData:responseData encoding: NSUTF8StringEncoding];
    NSInteger response = [responseString integerValue];
    [responseString release];
    return (response == 0);
}

- (NSString *)encode:(const uint8_t *)input length:(NSInteger)length {
    static char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 /=";

    NSMutableData *data = [NSMutableData dataWithLength:((length   2) / 3) * 4];
    uint8_t *output = (uint8_t *)data.mutableBytes;

    for (NSInteger i = 0; i > 18) & 0x3F];
        output[index   1] =                    table[(value >> 12) & 0x3F];
        output[index   2] = (i   1) > 6)  & 0x3F] : '=';
        output[index   3] = (i   2) > 0)  & 0x3F] : '=';
    }

    return [[[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding] autorelease];
}

Additionally, the following PHP code can be used on your server to handle receipt validation and record the transaction:

$receipt = json_encode(array("receipt-data" => $_GET["receipt"]));
// NOTE: use "buy" vs "sandbox" in production.
$url = "https://sandbox.itunes.apple.com/verifyReceipt";
$response_json = call-your-http-post-here($url, $receipt);
$response = json_decode($response_json);

// Save the data here!

echo $response->status;

Remember to replace "call-your-http-post-here" with your preferred HTTP post mechanism. By implementing this code and ensuring its accuracy, you can effectively verify receipt purchases and manage in-app transactions with confidence.