PHP中__construct(),类的构造函数详解
PHP中把以两个下划线__开头的方法称为魔术方法(Magic methods),这些方法在PHP中充当了举足轻重的作用。
__construct(),类的构造函数
php中构造方法是对象创建完成后第一个被对象自动调用的方法。在每个类中都有一个构造方法,如果没有显示地声明它,那么类中都会默认存在一个没有参数且内容为空的构造方法。
1、 构造方法的作用
通常构造方法被用来执行一些有用的初始化任务,如对成员属性在创建对象时赋予初始值。
2、 构造方法的在类中的声明格式
function __constrct([参数列表]){ 方法体 //通常用来对成员属性进行初始化赋值 }
3、 在类中声明构造方法需要注意的事项
1、在同一个类中只能声明一个构造方法,原因是,PHP不支持构造函数重载。
2、构造方法名称是以两个下画线开始的__construct()
下面是它的例子:
<?php class Person { public $name; public $age; public $sex; /** * 显示声明一个构造方法且带参数 */ public function __construct($name="", $sex="男", $age=22) { $this->name = $name; $this->sex = $sex; $this->age = $age; } /** * say 方法 */ public function say() { echo "我叫:" . $this->name . ",性别:" . $this->sex . ",年龄:" . $this->age; } }
创建对象$Person1且不带任参数
$Person1 = new Person(); echo $Person1->say(); //输出:我叫:,性别:男,年龄:27
创建对象$Person2且带参数“小明”
$Person2 = new Person("小明"); echo $Person2->say(); //输出:我叫:张三,性别:男,年龄:27
创建对象$Person3且带三个参数
$Person3 = new Person("李四","男",25); echo $Person3->say(); //输出:我叫:李四,性别:男,年龄:25

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