Required Products {#wc-req-prerequisites}
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`Visa Acceptance Solutions` `Unified Checkout` must be enabled and configured for your transacting merchant ID. See the [*Unified Checkout Developer Guide*](https://developer.cybersource.com/docs/cybs/en-us/unified-checkout/developer/all/rest/unified-checkout/uc-intro-setup.md "").  
You must also have a REST shared secret key and a Response MLE certificate. See the [*Getting Started with the REST API*](https://developer.cybersource.com/docs/cybs/en-us/platform/developer/all/rest/rest-getting-started/restgs-jwt-shared-secret-intro/restgs-mle-shared-secret-intro.md#restgs-security-mle-shared-secret-reply "") guide and the [*Getting Started with the REST API*](https://developer.cybersource.com/docs/cybs/en-us/platform/developer/all/rest/rest-getting-started/restgs-http-message-intro/restgs-security-key-pair-intro/restgs-security-key-pair-task.md "") guide.  
**Environment Prerequisite**  
The GMP PHP extension must be enabled on your MAMP or XAMPP server for JSON Web Token messaging.