php调用对象的方法

<?php
namespace app\php;
class a
{
 static $q = 888;
 public function index()
 {
 echo "1111";
 }
 
 static function debug()
 {
 echo "<br/>";
 echo 555;
 }
}

<?php
namespace app\php;
include "./a.php";
class b
{
 public function b()
 {
 echo 111;
 }
}
 $b = new b();
$b ->b();
$a = new a();
$a ->index();
echo $a::$q;
$a::debug();