php__clone()克隆方法以及淺克隆和深克隆使用實例詳解

可以在物件類別中定義一個clone()方法來調整物件的複製行為。此方法的程式碼將在克隆操作期間執行。除了將所有現有物件成員複製到目標物件之外，還會執行clone()方法指定的操作。下面修改Corporate_Drone類，增加以下方法：

function clone() { 
 $this->tiecolor = "blue";
}

之後，建立一個新的Corporate_Drone對象，增加employeeid成員的值，克隆這個對象，然後輸出一些數據，從而顯示克隆對象的tiecolor確實是透過clone()方法設定的。範例程式碼：

<?php
 // Create new corporatedrone object
  $drone1 = new corporatedrone();
 
 // Set the $drone1 employeeid member
  $drone1->setEmployeeID("12345");
 
 // Clone the $drone1 object
  $drone2 = clone $drone1;
 
 // Set the $drone2 employeeid member
  $drone2->setEmployeeID("67890");
 
 // Output the $drone1 and $drone2 employeeid members
  echo "drone1 employeeID: ".$drone1->getEmployeeID()."<br />";
  echo "drone2 employeeID: ".$drone2->getEmployeeID()."<br />";
  echo "drone2 tiecolor: ".$drone2->getTiecolor()."<br />";
?>

程式運行結果

drone1 employeeID: 12345
drone2 employeeID: 67890
drone2 tiecolor:

再來一個小範例：

<?php
class Fruit {
 private $name = "水果";
 private $color = "颜色";
 
 public function setName($name){
 $this->name = $name;
 }
 
 public function setColor($color){
 $this->color = $color;
 }
 
 function showColor(){
 return $this->color.&#39;的&#39;.$this->name."<br />";
 }
 
 function destruct(){
 echo "被吃掉了（对象被回收） <br />"; 
 }
}

$apple = new Fruit();
$apple->setName("大苹果");
$apple->setColor("红色");
echo $apple->showColor();

$clone_apple = $apple;
$clone_apple->setName("小苹果");
$clone_apple->setColor("青色");

echo $clone_apple->showColor();
?>

上面只是將一個類別賦值給另一個類，所以此時記憶體中仍是一個對象。

<?php
class Fruit {
 private $name = "水果";
 private $color = "颜色";
 
 public function setName($name){
 $this->name = $name;
 }
 
 public function setColor($color){
 $this->color = $color;
 }
 
 function showColor(){
 return $this->color.&#39;的&#39;.$this->name."<br />";
 }
 
 function destruct(){
 echo "被吃掉了（对象被回收） <br />"; 
 }
 function clone(){
 $this->name = "克隆水果"; 
 }
}

$apple = new Fruit();
$apple->setName("大苹果");
$apple->setColor("红色");
echo $apple->showColor();

$clone_apple = clone $apple;
$clone_apple->setColor("青色");

echo $clone_apple->showColor();
?>

clone方法克隆出了一個新的類，所以此時記憶體中有兩個物件。

php的clone()方法對一個物件實例進行的淺複製,物件內的基本數值類型進行的是傳值複製，而物件內的物件型成員變數,如果不重寫clone方法,顯式的clone這個物件成員變數的話,這個成員變數就是傳引用複製,而不是產生一個新的物件.如下面一個例子的第28行註釋所說

<?php
  class Account {
    public $balance;
    
    public function construct($balance) {
      $this->balance = $balance;
    }
  }
 
  class Person {
    private $id;
    private $name;
    private $age;
    public $account;
    
    public function construct($name, $age, Account $account) {
      $this->name = $name;
      $this->age = $age;
      $this->account = $account;
    }
    
    public function setId($id) {
      $this->id = $id;
    }
    
    public function clone() {  #复制方法,可在里面定义再clone是进行的操作
      $this->id = 0;
      $this->account = clone $this->account;  #不加这一句,account在clone是会只被复制引用,其中一个account的balance被修改另一个也同样会被修改
    }
  }
  
  $person = new Person("peter", 15, new Account(1000));
  $person->setId(1);
  $person2 = clone $person;
  
  $person2->account->balance = 250;
  
  var_dump($person, $person2);
  
 ?>

淺克隆：只是克隆物件中的非物件非資源數據，即物件中屬性儲存的是物件類型，則會出現克隆不完全

<?php
class B{
 public $val = 10;
}
class A{
 public $val = 20;
 public $b;
 public function construct(){
  $this->b = new B();
 }
}
$obj_a = new A();
$obj_b = clone $obj_a;
$obj_a->val = 30;
$obj_a->b->val = 40;
var_dump($obj_a);
echo &#39;<br>&#39;;
var_dump($obj_b);

運行結果如下：

object(A)[1]
 public 'val' => int 30
 public 'b' =>
 object(B)[2]
  public 'val' => int 40
 
object(A)[3]
 public 'val' => int 20
 public 'b' =>
 object(B)[2]
  public 'val' => int 40

深克隆：一個物件的所有屬性資料都徹底的複製，需要使用魔術方法clone()，並在裡面實作深度複製

<?php
class B{
 public $val = 10;
}
class A{
 public $val = 20;
 public $b;
 public function construct(){
  $this->b = new B();
 }
 public function clone(){
  $this->b = clone $this->b;
 }
}
$obj_a = new A();
$obj_b = clone $obj_a;
$obj_a->val = 30;
$obj_a->b->val = 40;
var_dump($obj_a);
echo &#39;<br>&#39;;
var_dump($obj_b);

運行結果如下：

object(A)[1]
 public 'val' => int 30
 public 'b' =>
 object(B)[2]
  public 'val' => int 40
 
object(A)[3]
 public 'val' => int 20
 public 'b' =>
 object(B)[4]
  public 'val' => int 10

以上是php__clone()克隆方法以及淺克隆和深克隆使用實例詳解的詳細內容。更多資訊請關注PHP中文網其他相關文章！