php class constant call $ this :: CONST

Question

爲什麼我可以從動態聲明中調用類常量？ 此代碼工作得很好：

echo $this::CONST; 

是不是錯了？

Answer 1

從http://php.net/manual/en/language.oop5.constants.php

<?php 
class MyClass 
{ 
    const CONSTANT = 'constant value'; 

    function showConstant() { 
     echo self::CONSTANT . "\n"; 
    } 
} 

echo MyClass::CONSTANT . "\n"; 

$classname = "MyClass"; 
echo $classname::CONSTANT . "\n"; // As of PHP 5.3.0 

$class = new MyClass(); 
$class->showConstant(); 

echo $class::CONSTANT."\n"; // As of PHP 5.3.0 
?> 

從動態宣言，呼籲恆定的作品一樣好從類