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PHP OOP - Class Constants
PHP - Class Constants
Class constants in PHP are fixed values that cannot be changed once they are defined.
Class constants are case-sensitive. However, it is recommended to name the constants in all uppercase letters.
Key Features of Class Constants:
- Declared using
constinside a class. - Cannot be changed after declaration.
- Do not use the
$symbol. - Accessed using
ClassName::CONSTANT_NAME. - Can be inherited but cannot be overridden.
Syntax
class ClassName {
const CONSTANT_NAME = value;
}
Defining and Accessing Class Constants
Example
<?php
class Car {
const WHEELS = 4; // Defining a constant
}
// Accessing the constant using the class name
echo "A car has " . Car::WHEELS . " wheels.<br>";
?>
Or, we can access a constant from inside the class by using the self keyword followed by the scope resolution operator (::) followed by the constant name, like here:
Example
<?php
class Car {
const WHEELS = 4; // Defining a constant
public function getWheels() {
return "This car has " . self::WHEELS . " wheels.";
}
}
// Accessing the constant using the class name
echo "A car has " . Car::WHEELS . " wheels.<br>";
// Accessing the constant using `self::` inside the class
$myCar = new Car();
echo $myCar->getWheels();
?>