PHP是弱变量的脚本语言，也就是说你无需先定义，这一点很灵活。也可以给予很大的自由度，但对于程序来说，自由并非好事。
因为给予后期维护人员阅读带来很大的麻烦。
下面来进入我们第一个程序:
1.php
////////////////////
＜?class helloWorld{
var $hellow_str = "Hello World!";
function helloWorld(){
echo $this-＞hellow_str;
}
}
$p = new helloWorld;
?＞
////////////////////
很明显，这是一个类，很简单的类，只有一个构造函数。目的就是输出"Hello World";首先我们定义了一个类成员变量，通过一个特殊的$this对象，输出该变量，oop思想我不是很精，仅仅在于php开发方面用到，其他的也只是借鉴，但是我想对于php开发者已经足够了。
接下来，解释下什么是$this对象，从这点我们先要知道什么是类。
类，可以解释为一群相同的群体，在类中的成员变量，如上面的$hellow_str可以看作是这个群体的独特的特征，比如，桌子群体是一个
类，桌子都有桌面，桌脚，这些“都有”的东西，就是桌子全体的共有特征，在程序类里面我们就可以定义其为 桌子类的一个成员变量。
////////////
class desktop{
var $desktop;#桌子面；
var $baluster;#桌子腿;
}
///////////
同样，在桌子世界里，他们也有共同的动作，比如移动[也许你现在就在推桌子^^]，也可能我们要把桌子的面子放大点，一样，这个就是桌子群提的共有方法了，[和特征近似哦，不过这是动作罢了]。让我们把这个共同特征加到类中去吧。
////////////////
class desktop{
var $desktop;#桌子面；
var $baluster;#桌子腿;
function move(){
#....
}
function largen(){
#...
}
}///////////////
知道了上面的，那么接下来就很好理解什么是$this对象了，没有错，他就是桌子群中的一个特定的对象，如果阁下还不能理解，那么，
我们接着解释。
如果，我们现在要对一张桌子进行整改，比如，我们想把桌子面积做的更大，那么，我们针对的就不是一群桌子，而是这个要整改的特定的桌子，这是个个体！所以，我们要把这个类进行“实例化”进行精确定位。因为，其他桌子我们不需要整改。
////////////////
class desktop{
var $desktop;#桌子面；
var $baluster;#桌子腿;
function move(){
#....
}
function largen(){
$this-＞desktop++;#放大桌子面
}
}
$d = new desktop;#“实例化，这个时候我们就是针对一个特定的桌子拉！
$d-＞largen();#哈哈，把这个特定桌子面放大点。其实$d = $this;明白吗，$d就是那个特定的桌子，$d-＞largen就是用那个特定桌子[桌子群大家都有的变大方法]把特定桌子面放大了点。
///////////////
原来，$this就是指一个特定桌子呀，哈哈，明白了，原来类是大家都有的属性，方法的集合，而一个特定的对象，就是这个群体中的一个个体，既然是他们当中的个体，当然拥有群体所拥有的共同特征和方法拉。
成员变量，成员方法[成员函数]，实例化，大家都知道了。
但是我桌子虽然想变大，可是我还不知道桌子开始有多大啊，这可能吗，怎么办呢？
接下来，我们隆重推出 构造函数 来拉。要说到构造函数啊，话多啊，就不多说了，他就是给我们桌子面和桌子腿确定大小的。
////////////////
class desktop{
var $desktop;#桌子面；
var $baluster;#桌子腿;
function desktop(){
$this-＞desktop = 100;
$this-＞baluster = 100;
}
function move(){
#....
}
function largen(){
$this-＞desktop++;#放大桌子面
}
}
////////////
看到了吧，我把桌子定义了大小和长度哦
//////////
聪明的你，一定想立即实例化了吧，如果我开始在定义成员变量里就给值了，那不是说所有桌子都一样大吗？
//////////////
class desktop{
var $desktop;#桌子面；
var $baluster;#桌子腿;
function desktop(){
$this-＞desktop = 100;
$this-＞baluster = 100;
}
function move(){
#....
}
function largen(){
$this-＞desktop++;#放大桌子面
}
}
$d = new desktop;
$d-＞desktop();
////////////////////
But the result is: Call to a member function desktop() on a non-object in
Unlucky, the author must be cheating on clicks, bs is so small, TT.
In fact I was wrong, I know I was wrong. It turns out that the function we just added
function desktop(){
$this-＞desktop = 100;
$this-＞baluster = 100;
}
It is a constructor. What is a constructor? Oops, it turns out that the constructor is a class-specific function. After the class is instantiated, the class will automatically execute the constructor in the first step, which is opening up a memory unit for the class.
In order to verify whether it is executed from the beginning, please focus on the first code in this tutorial. Wow, you see a method and a constructor with the same name as the class. We have already output the code after instantiation, which proves that I am not wrong yet.
Okay, back to our table world, you found that all the table tops and legs are 100 at this time.
2.php
Execution code
//////////////
＜?
class desktop{
var $desktop;#Desktop;
var $baluster;#Table legs;
function desktop(){
$this-＞desktop = 100; $this-＞desktop."Size!＜br /＞";
}
function move(){
#....
}
function largen(){
$this-＞desktop++;#Enlarge the desktop
echo "7~, I renovated the small desk today, so I won’t blame you, haha, I have more face than you now, I have ".$this-＞desktop." "Quack";
}
}
$d = new desktop;
$d-＞largen();
?＞
Small table, escaped from the table family, Because our reputation is not as big as that of a small table. The old man at the table can't stand it any more. It's up to me to show you the demo.
//////////////
＜?
class desktop{
var $desktop;#Desktop;
var $baluster;#Table legs;
function desktop($desktop){
$this-＞desktop = $desktop;
$this-＞baluster = 100;
echo "Our desk family orders everyone to give me the same face on the table In ".$this-＞desktop." size!
$this-＞desktop++;#Enlarge the desktop
echo "7~, I renovated the small desk today, so I don’t mind you, haha, I have more face than you now, I have".$this-＞ desktop."Gaga";
}
}
$d = new desktop;
$d-＞largen();
?＞
Small table, turn left I turned, turned right and looked around for a long time. I was tired of shopping and felt that I had evolved now and it was time to see the new kind. So after the table transformation was executed, I found...
/////
$d = new desktop(101);
////
My tmd is still a small table.
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http: //www.bkjia.com/PHPjc/317374.htmlTechArticlePHP is a weak variable scripting language, which means you don’t need to define it first, which is very flexible. A lot of freedom can also be given, but freedom is not a good thing for a program. Because after giving...
