PHP 클래스의 상수 사용 예

class Employee {
    //定义常量
    const AVAILABLE      = 0;
    const OUT_OF_STOCK   = 1;
    public $status;
}
print Employee::AVAILABLE;
?>

例2，定义类中的常量

   class math_functions {
    //定义常量
     const PI = '3.14159265';
     const E = '2.7182818284';
     const EULER = '0.5772156649';
     /* 在这里定义其它的常量与方法... */
   }
   echo math_functions::PI;
?>