PHP const와 정적 변수의 차이점은 무엇입니까

class staticTest1 { var $var1 = "hello"; public static $var2 = "hellostatic"; //public, protected, private const var3 = "helloconst"; public static function displayDifferent(){ ### echo $this->$var1."
";//不能访问普通变量 echo staticTest1::$var2."
";//可以访问类的静态变量 echo self::var3."
";//不能用$this::var3, self::var3代表当前类，$this::var3代表当前对象 } }

//第一种，通过对象调用 $test1 = new staticTest1(); echo $test1->displayDifferent(); echo "
"; //第二种，通过类调用 echo staticTest1::displayDifferent(); echo "
";

class constTest1 { var $var1 = "welcome"; // public const pi = 3.14;//不能加修饰权限 const pi = 3.14; // const function displayDifferent() {//function前不能加const // // } function displayDifferent() { echo self::pi."
"; // echo $this::pi."
"; } static function displayDifferent2() { echo self::pi."
"; // echo $this::pi."
"; //这句话不行。 } }

//第一种，通过对象调用 $test2 = new constTest1(); echo $test2->displayDifferent(); //第二种，通过类调用 //echo constTest1::displayDifferent();//对象名用"::"只能访问静态变量和方法,所以这个不行 echo constTest1::displayDifferent2();