2个父级和子级类的新实例，需要直接在父级中更改父级变量，并在子级中查看

问题描述

| 的PHP 如果创建父类的新实例和子类的新实例，如何直接在父类中更改变量并查看子类中的更改？ 采取以下代码：

class parentClass {

    public $vara = \'dojo\';

    public function setvarA() {
        $this->vara = \'something grand\';
    }

    public function getvarA() {
        return $this->vara;
    }

}

class childClass extends parentClass {

    public function useVara() {
        echo parent::getvarA();
    }

}

$parentInstance = new parentClass();
$childInstance = new childClass();

$initialVara = $parentInstance->getvarA(); // should set $initialVara variable to \'dojo\'

$childInstance->useVara(); // should echo \'dojo\'

$parentInstance->setvarA(); // should set $vara to \'something grand\'

$changedVara = $parentInstance->getvarA(); // should set $changedVara variable to \'something grand\'

$childInstance->useVara(); // should echo \'something grand\' but fails to do so...how can I do this?

    

解决方法

        如果父级中有

private

或

protected

变量（成员），则可以从子类中像下面这样简单地访问它：

$this->varA = ‘something’;

您的子方法无法反映更改的原因是，子方法和父方法是单独的内存空间中的两个不同的对象。如果您希望他们分享价值，可以将其设为

static

。 您无需声明

public

。

class Parent {
    private $varA;
    protected $varB;
    public $varC;

    protected static $varD;

    public function getD() {
        return self::$varD;
    }

    public function setD($value) {
        self::$varD = $value;
    }
}

class Child extends Parent {

    public function getA() {
        return $this->varA;
    }

    public function getB() {
        return $this->varB;
    }

    public function getC() {
        return $this->varC;
    }

 }

 $child = new Child();

 $child->getA(); // Will not work since $varA is private to Parent
 $child->getB(); // Works fine because $varB is accessible by Parent and subclasses
 $child->getC(); // Works fine but ...
 $child->varC;   // .. will also work.
 $child->getD(); // Will work and reflect any changes to the parent or child.

如果您不希望父类的所有实例共享值。您可以将父项或子项传递给新实例，然后传递并相应地更新所有相关对象的值。

$parent->addChild(new Child());

并在set方法中：

$this->varA = $value;
foreach ($this->children as $child) {
     $child->setVarA($value);
}

希望这会有所帮助。