Trigger user_create hook in Roundcube API in PHP

I would like to implement user_create hook of Roundcube.

I do have PHP portal where someone registers first time i would like create user for him/her in the Roundcube by using Roundcube API.

Lets say user with the details name, email, phonenumber, address has been registered.

So API call will be triggering to mail server using Roundcube API by sending email that create email account for requested email address.

Does any one having any idea how to use using PHP language?