下面是PHP中对象的继承的判断代码：

class Foo {
public $foobar = 'Foo';

public function test() {
echo $this->foobar . "\n";
}
}

class Bar extends Foo {
public $foobar = 'Bar';
}

$a = new Foo();
$b = new Bar();

echo "use of test() method\n";
$a->test();
$b->test();

echo "instanceof Foo\n";
var_dump($a instanceof Foo); // TRUE
var_dump($b instanceof Foo); // TRUE

echo "instanceof Bar\n";
var_dump($a instanceof Bar); // FALSE
var_dump($b instanceof Bar); // TRUE

echo "subclass of Foo\n";
var_dump(is_subclass_of($a, 'Foo')); // FALSE
var_dump(is_subclass_of($b, 'Foo')); // TRUE

echo "subclass of Bar\n";
var_dump(is_subclass_of($a, 'Bar')); // FALSE
var_dump(is_subclass_of($b, 'Bar')); // FALSE
?>