Edit file File name : app.json Content :{ "name": "Braintree PHP Example", "description": "An example Braintree integration for PHP", "keywords": ["braintree", "php"], "website": "https://www.braintreepayments.com", "repository": "https://github.com/braintree/braintree_php_example", "logo": "https://avatars1.githubusercontent.com/u/3453", "success_url": "/", "env": { "BT_ENVIRONMENT": { "description": "Run against Braintree sandbox environment", "required": true, "value": "sandbox" }, "BT_MERCHANT_ID": { "description": "Your Braintree Merchant ID", "required": true }, "BT_PUBLIC_KEY": { "description": "Your Braintree Public Key", "required": true }, "BT_PRIVATE_KEY": { "description": "Your Braintree Private Key", "required": true } } } Save