PHP：从父方法中的静态方法调用子构造函数

我希望在父类中有一个静态方法,它创建我调用此方法的子类的实例.

一个让这个更清晰的例子：

class parent {
    public static method make_objects($conditions){
        for (...){
            // here i want to create an instance
            // of whatever subclass i am calling make_objects on
            // based on certain $conditions
        }
    }
}

class sub extends parent{
    ...
}

$objects = sub::make_objects($some_conditions);

从PHP 5.3开始,您可以使用 static关键字

<?PHP
class A {
  public static function newInstance() {
    $rv = new static();  
    return $rv;
  }
}
class B extends A { }
class C extends B { }

$o = A::newInstance(); var_dump($o);
$o = B::newInstance(); var_dump($o);
$o = C::newInstance(); var_dump($o);

版画

object(A)#1 (0) {
}
object(B)#2 (0) {
}
object(C)#1 (0) {
}

编辑：另一个(类似的)例子

<?PHP
class A {
  public static function newInstance() {
    $rv = new static();  
    return $rv;
  }

  public function __construct() { echo " A::__construct\n"; }
}
class B extends A {
  public function __construct() { echo " B::__construct\n"; }
}
class C extends B {
  public function __construct() { echo " C::__construct\n"; }   
}

$types = array('A','B','C');
foreach( $types as $t ) {
  echo 't=',$t,"\n";
  $o = $t::newInstance();
  echo '  type of o=',get_class($o),"\n";
}

版画

t=A
 A::__construct
  type of o=A
t=B
 B::__construct
  type of o=B
t=C
 C::__construct
  type of o=C

原文地址：https://www.jb51.cc/php/137397.html