Php REST API backed up with a MySQL database is a very common schematic of an Enterprise mobile application. When the scenario requires data to be stored in a centralize manner, then this architecture should be used. Otherwise, the local database in the mobile can be used for storage and retrieval of information.
Get Android source code here: https://github.com/delaroy/FragranceCart/tree/Webservices
Get PHP source code here: https://www.dropbox.com/s/eob6p9su51t6wsz/fragrances.zip?dl=0