1.当将所有实例设为null,php会自动清除对象的引用。
2.建构子:__construct()
清除对象时自动执行的方法:__destruct()
也可以设置手动清除对象的方法:destroy或者clean_up
3.对象中的三种变量范围:public、private和protected。
4.对象中的常量属性可以使用const关键字,然后在对象外部以“对象名::属性名”的格式引用,在对象内部以“self::属性名”的格式引用。
5.在整个对象所有实例中通用的属性,就是静态属性,使用static关键字。
static与const的区别在于,const前只能使用public关键字,而static可以使用其他关键字。此外,static属性并非只读。
6.在整个对象所有实例中通用的方法,就是静态方法,也使用static关键字。
7.可以定义一个抽象类,用来定义界面。这种类只能被继承,而不能创造实例。在类内部,用abstract定义子类必须提供的方法。
凡是有abstract方法的类,必须在类名前使用abstract关键字。
abstract class Producr
8.在方法前加final关键字,可以防止子类override这个方法。
类名之前也可以加final关键字,这样就表明其他类不能继承它。
9.界面interface用来定义一系列抽象类的结构。
interface IProduct
{
... ...
}
abstract class Product implements Iproduct
{
......
}
10.
== 比较两个对象是否为同样类型,以及是否有同样的值。
=== 比较两个对象是否为同一个类的实例。
11.类的克隆:完全复制值。
$a = new SomeClass();
$b = clone $a;
可以定义一个__clone()函数,专门对克隆行为进行定制。
12.可以定义一个类的__toString()方法,对使用print和echo函数的行为进行定制。
13.get_class()函数:返回一个对象的类名。
14.可以在一个函数的参数前加类名,表示TypeHint。
15.可以定义一个__autoload()函数,它的参数就是php找不到定义的类名。可以在这个函数中定义如何自动加载。

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