Site technologies for working with a mobile application?

Question

Mobile development

Good day,
what are the practices/recommendations/rules when developing a site in php-mysql (site-catalog) so that later you can easily and correctly create a mobile application for it?
For example: work through REST, a specific database, hosting, php-framework (phalconphp) and so on.
And if all / some points are not taken into account, is it always possible to make a REST-API through a microservice, or is it better to do just that?
Thank you.