Set up a sub domain and also a custom domain feature in a saas app with PHP and MySQL

I need to offer on my saas app built it with PHP and MySQL a subdomain and custom domain feature, is a like a website builder where the customer upload images and text and choose a theme, then he can see their website in: [login to view URL] - I need that the customer have in first instance a subdomain name like: [login to view URL] - Also I need that he could enter a custom domain in some screen in our app , save it and point the domain with an A or CNAME record in the control panel of his domain provider, then he could see the website in: [login to view URL] I have: - A VPS with root access - The Web app in PHP with a custom framework and mysql for database. I have 2 databases, one for customer information and another with notifications, transactions, etc, high volume of data. - The images of every customer are under 1 single shared folder, the app resolves the call of every piece of information for every customer. I need to know: - What do you need to acomplish this project? I want: - Only the subdomain and custom domains feature connected to my app with the configuration in virtualhost, etc. I can provide the screen for the feature. - If we can setup this via skype in a session or more it woukd be better.