PHP Constant Class

The const keyword is used to declare a class constant. A constant is unchangeable once it is declared. The constant class declared inside the class definition. The class constant is case-sensitive. However, it is recommended to name the constants in all uppercase letters. Constant differ from normal variables as no $ (dollar sign) is used. The default visibility of class constants is public. Class constants are useful when you need to declare some constant data (which does not change) within a class.

There are two ways to access class constant:

1. Outside the Class: The class constant is accessed by using the class name followed by the scope resolution operator (::) followed by the constant name.

Example:

<?php

class code{

    // Declare const class
    const Greetings = "Welcome to geeksforgeeks";
}

// Access const class
echo code::Greetings
?>

Output:

Welcome to geeksforgeeks

2. Inside the Class: It can be accessed by using the self keyword followed by the scope resolution operator(::) followed by the constant name.

Example:

<?php

class code{

    // Declare const class
    const Greetings = "Welcome to geeksforgeeks";
          
    public function welcome(){
        echo self::Greetings;
    } 
}

// Access const class
$val = new code();
$val->welcome();

?>

Output:

Welcome to geeksforgeeks