关键点在于一个是静态绑定，一个是延迟绑定
<?php
class A
{
public function __construct() {
}
public function createObjStatic() {
$obj = new self();
$obj->say();
}
public function createObjDynamic() {
$obj = new static();
$obj->say();
}
public function say() {
echo "I'm class A.";
}
}
class B extends A
{
public function __construct() {
}
public function say() {
echo "I'm class B.";
}
}
$B = new B();
$B->createObjDynamic();
echo "<BR>";
$B->createObjStatic();
?>