php中对象的引用、浅复制、深复制

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概念

引用: 对象之间的等号赋值是引用赋值，两者是同一个资源
浅复制: 值赋值。所有的引用属性(如对象属性)仍然是一个指向原来变量的引用
深复制: 所有引用属性指向复制过来的新对象

测试

引用

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class A{
    public $obj;
    public $name='A';
    public function __construct(){
        $this->obj = new B();
    }
}
class B{
    public $name='B';
}
$a = new A();
$b = $a;
var_dump($a,$b);    //引用 两者完全相同
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//结果
class A#1 (2) {
  public $obj =>
  class B#2 (1) {
    public $name =>
    string(1) "B"
  }
  public $name =>
  string(1) "A"
}
class A#1 (2) {
  public $obj =>
  class B#2 (1) {
    public $name =>
    string(1) "B"
  }
  public $name =>
  string(1) "A"
}

浅复制

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$b = clone $a;
var_dump($a,$b);    //浅复制 $b中的obj依旧指向$a中的obj
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//结果
class A#1 (2) {
  public $obj =>
  class B#2 (1) {
    public $name =>
    string(1) "B"
  }
  public $name =>
  string(1) "A"
}
class A#3 (2) {
  public $obj =>
  class B#2 (1) {
    public $name =>
    string(1) "B"
  }
  public $name =>
  string(1) "A"
}

深复制

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class A{
    public $obj;
    public $name='A';
    public function __construct(){
        $this->obj = new B();
    }
    public function __clone(){
        $this->obj = new B();
    }
}
class B{
    public $name='B';
}
$a = new A();
$b = clone $a;
var_dump($a,$b);    //深复制 $b中的obj依旧指向$a中的obj
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//结果
class A#1 (2) {
  public $obj =>
  class B#2 (1) {
    public $name =>
    string(1) "B"
  }
  public $name =>
  string(1) "A"
}
class A#3 (2) {
  public $obj =>
  class B#4 (1) {
    public $name =>
    string(1) "B"
  }
  public $name =>
  string(1) "A"
}