A data type can be described as being either: A built-in data type, such as an int or char, etc.
A user-defined data type, such as a class or interface.
Data types can also be defined as being either: Value Types (C# Reference), which store values and Reference Types (C# Reference), which store references to the actual data.
This is very interesting part of a programming language. In C++ you write
wchar_t but in C# you write
In Visual FoxPro you write
Logical but in C# you write
To get more out of it you can go through this link
Data Types Compared in Different Languages
Well you did not have any idea of PHP here but the thing is in PHP you don’t have to declare data type here.
Whether its an advantage or disadvantage you decide.