1
<?
php

2
/*
*

3
* 单例模式

4
*

5
* 保证一个类仅有一个实例,并提供一个访问它的全局访问点

6
*

7
*/


8
class
Singleton

9
{

10
static
private
$_instance
=
null
;

11


12
private
function
__construct()

13
{

14
}

15


16
static
public
function
getInstance()

17
{

18
if
(
is_null
(self
::
$_instance
)) {

19
self
::
$_instance
=
new
Singleton();

20
}

21
return
self
::
$_instance
;

22
}

23


24
public
function
display()

25
{

26
echo
“
it is a singlton class function
“
;

27
}

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}

29


30
//
$obj = new Singleton(); // 声明不能成功


31
$obj
=
Singleton
::
getInstance();

32
var_dump
(
$obj
);

33
$obj
->
display();

34


35
$obj1
=
Singleton
::
getInstance();

36
var_dump
((
$obj
===
$obj1
));