Write an interface with PHP, randomly generate 6 digits, and then send them to the corresponding mobile phone number in the form of short messages. I haven't written the interface and I don't know how

Write an interface with PHP, randomly generate 6 digits, and then send them to the corresponding mobile phone number in the form of short messages. I haven't written the interface and I don't know how to write it. The SMS interface requires you to have a corresponding SMS service provider, usually a third-party SMS service provider. This service is usually charged. The more you charge, the more messages you can send every day.

You need to apply to them for a short message interface. After the successful application, there will be an interface document, and you can send the corresponding data according to the provisions in the document. The data usually sent includes: mobile phone number and the content of the short message to be sent.

Interfaces are generally written in documents, and even some documents will be accompanied by examples for developers' reference.