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:
- 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
<?php   class code{       // Declare const class     const Greetings = "Welcome to neveropen"; }   // Access const class echo code::Greetings ?> |
Output:
Welcome to neveropen
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
<?php   class code{       // Declare const class     const Greetings = "Welcome to neveropen";                 public function welcome(){         echo self::Greetings;     } }   // Access const class $val = new code(); $val->welcome();   ?> |
Output:
Welcome to neveropen
