PHP函数——is_subclass_of() 函数 判断一个对象是否为一个类的子类

说明：

bool is_subclass_of ( object $object , string $class_name )

如果对象 object所属类是类 class_name的子类，则返回 TRUE ，否则返回 FALSE 。

例子：

 // define a class
 class  WidgetFactory
 {
  var  $oink  =  'moo' ;
}

// define a child class
 class  WidgetFactory_Child  extends  WidgetFactory
 {
  var  $oink  =  'oink' ;
}

// create a new object
 $WF  = new  WidgetFactory ();
 $WFC  = new  WidgetFactory_Child ();

if ( is_subclass_of ( $WFC ,  'WidgetFactory' )) {
  echo  "yes,  WFC  is a subclass of WidgetFactory\n" ;
} else {
  echo  "no,  WFC  is not a subclass of WidgetFactory\n" ;
}

if ( is_subclass_of ( $WF ,  'WidgetFactory' )) {
  echo  "yes,  WF  is a subclass of WidgetFactory\n" ;
} else {
  echo  "no,  WF  is not a subclass of WidgetFactory\n" ;
}

// usable only since PHP 5.0.3
 if ( is_subclass_of ( 'WidgetFactory_Child' ,  'WidgetFactory' )) {
  echo  "yes, WidgetFactory_Child is a subclass of WidgetFactory\n" ;
} else {
  echo  "no, WidgetFactory_Child is not a subclass of WidgetFactory\n" ;
} 

运行结果：

yes, WFC is a subclass of WidgetFactory
no, WF is not a subclass of WidgetFactory
yes, WidgetFactory_Child is a subclass of WidgetFactory

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