PHP OOP Class Constants
PHP OOP Class Constants
You define it using the keyword:
1. Basic Class Constant Example
Output:
Hello World
Note: You access constants using :: (Scope Resolution Operator)
No need to create an object.
2. Constants Inside Object
Even if constants belong to class, you can access using object:
But preferred is:
3. Multiple Constants in a Class
4. Constants Are Always Public
Class constants:
- Cannot be private
- Cannot be protected
- Visibility modifiers are NOT allowed
This is valid in PHP 7.1+:
But older PHP versions only allow:
5. Constants vs Variables
| Feature | Constant | Property (Variable) |
|---|---|---|
| Defined using | const | public $name |
| Change value | No | Yes |
| Access using | ClassName::CONST | $obj->property |
| Memory | Fixed | Depends |
| Object required | No | Yes |
6. Constants with Inheritance
A child class can access parent constants.
7. Overriding Constants
A child class can redefine (override) constants.
8. Use Class Name Dynamically
9. Practical Use Case of Class Constants
Example: Application configuration
Example: Product Types
Summary (Easy to Remember)
| Feature | Meaning |
|---|---|
const | Create constant inside class |
| Access | ClassName::CONST_NAME |
| No object needed | Yes |
| Cannot change value | Yes |
| Used for fixed data | Yes |
