关于trait

Question

<?php
trait T{
    static function myDefault(){return "T::Default ";}
    static public function myPublic(){return "T::Public ";}
    static protected function myProtected(){return "T::Protected ";}
    static private function myPrivate(){return "T::Private ";}
    function testT1(){
        echo T::myDefault();
        echo T::myPublic();
        //echo T::myProtected();//error，不解
        //echo T::myPrivate();//error，不解
    }
    function testT2(){
        echo self::myDefault();
        echo self::myPublic();
        echo self::myProtected();
        echo self::myPrivate();
    }
    function testT3(){
        echo $this::myDefault();
        echo $this::myPublic();
        echo $this::myProtected();
        echo $this::myPrivate();
    }
    function testT4(){
        echo static::myDefault();
        echo static::myPublic();
        echo static::myProtected();
        echo static::myPrivate();
    }
}
class A{
    use T;
    function testA1(){
        echo T::myDefault();
        echo T::myPublic();
        //echo T::myProtected();//error，不解
        //echo T::myPrivate();//error，不解
    }
    function testA2(){
        echo A::myDefault();
        echo A::myPublic();
        echo A::myProtected();
        echo A::myPrivate();
    }
    function testA3(){
        echo self::myDefault();
        echo self::myPublic();
        echo self::myProtected();
        echo self::myPrivate();
    }
    function testA4(){
        echo $this::myDefault();
        echo $this::myPublic();
        echo $this::myProtected();
        echo $this::myPrivate();
    }
    function testA5(){
        echo static::myDefault();
        echo static::myPublic();
        echo static::myProtected();
        echo static::myPrivate();
    }    
}
echo A::myDefault();
echo A::myPublic();    
//echo A::myProtected();//error
//echo A::myPrivate();//error
$obj = new A;
echo $obj::myDefault();
echo $obj::myPublic();
//echo $obj::myProtected();//error
//echo $obj::myPrivate();//error
echo "<br/>";$obj->testT1();
echo "<br/>";$obj->testT2();
echo "<br/>";$obj->testT3();
echo "<br/>";$obj->testT4();
echo "<br/>";$obj->testA1();
echo "<br/>";$obj->testA2();
echo "<br/>";$obj->testA3();
echo "<br/>";$obj->testA4();
echo "<br/>";$obj->testA5();
?>

Answer 1

不要用T，用self

• trait是不能实例化的，可以理解为介于(?)interface和abstract class之间
• 引用自身的常量或者静态方法之类的建议用self