关于php全局自定义变量的求解！

$a="123";class dd{   function show(){     global $a;     $a="cc";   }}class cc{   function show(){     global $a;     return $a;   }}$d= new dd();$d-> show();$c= new cc();echo $c-> show();

<?php//父类class BaseClass {	public static $name = "";	public function __construct(){	}}//子类一class son1Class extends BaseClass{	public function initName($name){		parent::$name = $name;	}}//子类二class son2Class extends BaseClass{	public function index(){		return parent::$name;	}}//实例化类一$a = new son1Class();//初始化$name$a->initName("PHPer");//实例化类二$b = new son2Class();//获取$name的值$name = $b->index();//在son1Class初始化一$name值，在son2Class中也是可以调用的...echo $name; //输出PHPer