دانلود کتاب آموزش برنامه نویسی PHP

The foundation of a flexible application is variability – the capability of the program to serve multiple purposes in different contexts. Variables are a common mechanism to build such flexibility in any programming language. They’re named placeholders that reference a specific value that a program wants to use. This could be a number, a raw string, or even a more complex object with its own properties and methods. The point is that a variable is the way a program (and the developer) references that value and passes it along from one part of the program to another.