Examples of usage of constants in php classes

class Employee {
 //Define constants
 const AVAILABLE = 0;
 const OUT_OF_STOCK = 1;
 public $status;
}
print Employee::AVAILABLE;
?>

Example 2, define constants in classes

 class math_functions {
 //Define constant
 const PI = '3.14159265';
 const E = '2.7182818284';
 const EULER = '0.57721 56649';
/ * Define other constants and methods here... */
 }
 echo math_functions::PI;
?>