PHP applications that work with persistent data mainly use two options for storing data: relational databases and the local file system. Relational databases are more suited for storing structured data, where applications access data based on some search condition. For example, employee information, which contains components like firstname, lastname, employeeid, and salary, should be stored in a relational database. An application can then access the employee information using firstname, lastname, employeeid, or salary as search criteria.
File systems are useful for storing simple data like configuration files and unstructured data like images or word processing documents. Here, the text editor application will access the data using the absolute path of the file where the data is stored.
In this chapter we will cover:
PHP's functions that allow us to store and retrieve data from the server's local file system
A complete online storage application, which stores all its data in files