PHP OOP - Class Constants

PHP - Class Constants

Class constants are useful if you need to define some constant data within a class.

A class constant has a fixed value, and cannot be changed once it is declared.

A class constant is declared inside a class with the const keyword.

The default visibility of class constants is public.

Class constants are case-sensitive. However, it is recommended to name the constants in all uppercase letters.

PHP - Access Class Constants

A class constant can be accessed in two ways:

• A constant can be accessed from outside the class by using the class name followed by the scope resolution operator (::) followed by the constant name:

Example

    <?php
class
    Goodbye {
  const MESSAGE = "Thank you for visiting example.com!";
}

echo
    Goodbye::MESSAGE; // Access constant

    ?>

• A constant can be accessed from inside the class by using the self keyword followed by the scope resolution operator (::) followed by the constant name:

Example

    <?php
class Goodbye {
  const MESSAGE = "Thank you for visiting example.com!";

 
    public function bye() {
    echo self::MESSAGE; // Access
    constant
 
    }
}

$goodbye = new Goodbye();
$goodbye->bye();
?>