Revealing the secrets of using PHP constructor_PHP tutorial

After a long period of development of PHP, many users know PHP very well. Here I will express my personal understanding and discuss it with everyone. Most classes have a special method called a constructor. When an object is created, it will automatically call the PHP constructor, that is, the constructor method will be automatically called when the new keyword is used to instantiate the object.

The declaration of the PHP constructor is the same as the declaration of other operations, except that its name must be __construct(). This is a change in PHP5. In previous versions, the name of the constructor must be the same as the class name. This can still be used in PHP5, but now few people use it. The advantage of this is that the constructor can be Independent of the class name, there is no need to change the corresponding constructor name when the class name changes. For backward compatibility, if there is no method named __construct() in a class, PHP will search for a constructor method written in php4 with the same name as the class name. Format: function __construct ([parameter]) { ... ... } Only one constructor method can be declared in a class, but the constructor method will only be called once every time an object is created. This method cannot be called actively, so usually Use it to perform some useful initialization tasks. For example, the corresponding properties are assigned initial values ​​when the object is created.

<ol class="dp-xml">
<li class="alt"><span><span>//创建一个人类  </span></span></li>
<li class=""><span> </span></li>
<li class="alt"><span>0class Person   </span></li>
<li class=""><span>0{   </span></li>
<li class="alt"><span>//下面是人的成员属性   </span></li>
<li class=""><span>var $name;       //人的名子   </span></li>
<li class="alt"><span>var $sex;        //人的性别   </span></li>
<li class=""><span>var $age;        //人的年龄   </span></li>
<li class="alt"><span>//定义一个构造方法参数为姓名$name、性别$sex和年龄$age   </span></li>
<li class=""><span>function __construct($name, $sex, $age)   </span></li>
<li class="alt"><span>{   </span></li>
<li class="">
<span>//通过构造方法传进来的$name给成员属性$this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>name赋初使值   </span>
</li>
<li class="alt">
<span>$this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span class="attribute"><font color="#ff0000">name</font></span><span>=$name;   </span>
</li>
<li class="">
<span>//通过构造方法传进来的$sex给成员属性$this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>sex赋初使值   </span>
</li>
<li class="alt">
<span>$this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span class="attribute"><font color="#ff0000">sex</font></span><span>=$sex;   </span>
</li>
<li class="">
<span>//通过构造方法传进来的$age给成员属性$this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>age赋初使值   </span>
</li>
<li class="alt">
<span>$this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span class="attribute"><font color="#ff0000">age</font></span><span>=$age;   </span>
</li>
<li class=""><span>}   </span></li>
<li class="alt"><span>//这个人的说话方法   </span></li>
<li class=""><span>function say()   </span></li>
<li class="alt"><span>{  </span></li>
<li class="">
<span>echo "我的名子叫：".$this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>name." 性别：".$this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>sex." 我的年龄是：".$this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>age."</span><strong><font color="#006699"><span class="tag"><</SPAN><SPAN class=tag-name>br</SPAN><SPAN class=tag>></span></font></strong><span>";   </span>
</li>
<li class="alt"><span>}   </span></li>
<li class=""><span>}   </span></li>
<li class="alt"><span>//通过构造方法创建3个对象$p1、p2、$p3,分别传入三个不同的实参为姓名、性别和年龄  </span></li>
<li class="">
<span>$</span><span class="attribute"><font color="#ff0000">p1</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">new</font></span><span> Person("张三","男", 20);   </span>
</li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">p2</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">new</font></span><span> Person("李四","女", 30);   </span>
</li>
<li class="">
<span>$</span><span class="attribute"><font color="#ff0000">p3</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">new</font></span><span> Person("王五","男", 40);   </span>
</li>
<li class="alt"><span>//下面访问$p1对象中的说话方法   </span></li>
<li class="">
<span>$p1-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>say();   </span>
</li>
<li class="alt"><span>//下面访问$p2对象中的说话方法   </span></li>
<li class="">
<span>$p2-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>say();   </span>
</li>
<li class="alt"><span>//下面访问$p3对象中的说话方法   </span></li>
<li class="">
<span>$p3-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>say();   </span>
</li>
</ol>

The output result is:
My name is: Zhang San Gender: Male My age is: 20
My name is: Li Si Gender: Female My age is: 30
My name is: Wang Wu Gender: Male My age is: 40

http://www.bkjia.com/PHPjc/446532.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/446532.htmlTechArticleAfter a long period of development of PHP, many users know PHP very well. Here I will express my personal understanding and share it with you. Discuss discuss. Most classes have a special method called a constructor. ...