Charge dynamic application fees based on card brand

connect_app_fee_by_card_brand.php

<?php 

// Include Stripe's library and set your API key. 
require('./config.php');

// Retrieve the account ID and amount details from your own database...
// Ex: $db is an object containing the attributes you retrieve from your database.

// Check for a submitted token
if (isset($_POST['stripeToken'])){
  // Retrieve the token from Stripe
  $token = \Stripe\Token::retrieve($_POST['stripeToken']);
  
  // Calculate the application fee based on the card brand
  if ($token->card->brand == "American Express"){
    // Charge a 3.5% application fee for American Express
    $application_fee = ($db->amount/100 * .035) * 100; 
  }
  else {
    // Charge 2.2% + $0.30 for everything else
    $application_fee = ($db->amount/100 * .022 + .30) * 100;
  }

  // Create the charge
  try {
    $charge = \Stripe\Charge::create(array(
      "amount" => $db->amount, // The total amount to charge the customer, in cents
      "currency" => "usd",
      "source" => $token, // The token submitted from Checkout or Stripe.js
      "application_fee" => $application_fee,
      "destination" => $db->connected_account_id, // The account ID, retrieved from your database
    ));
    $success = "Thanks! Your payment has been made";
  }
  catch(\Stripe\Error\Card $e) {
    // Since it's a decline, \Stripe\Error\Card will be caught
    $body = $e->getJsonBody();
    $error  = $body['error']['message']; // Display the $error message to the user in your app
  } catch (\Stripe\Error\RateLimit $e) {
    // Rate limits are pretty rare. Maybe have the user try again?
  } catch (\Stripe\Error\InvalidRequest $e) {
    // You made an invalid request to Stripe. Maybe log or send yourself an email?
  } catch (\Stripe\Error\Authentication $e) {
    // You used a bad API key
  } catch (\Stripe\Error\ApiConnection $e) {
    // There was a connectivity problem. Maybe log and have the user try again?
  } catch (\Stripe\Error\Base $e) {
    // Some other API error. Maybe log or send yourself an email?
  } catch (Exception $e) {
    // Something unrelated to Stripe happened. Log or send yourself an email, etc
  }
}