How to request Azure Key Vault to sign a JSON with a secret

I would like to create a code where I request Azure Key Vault to sign a JSON containing data and return the hash of the signed data with the secret. I will send this hash to an external API, and the API will 'unsign' the hash with the public part of the secret (Note: my secret is actually a private key). The purpose of this code is to ensure that the entity sending data to the external API does not have access to the value of my private key (secret). If anyone can explain the step-by-step process of this functionality or provide documentation, I would be very grateful. The language I am using is PHP, but it can be an example in Python as well.