PHP入门 - 面向对象

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类的声明

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class Hello {
    public function sayello() {
        echo 'Hello PHP';
    }
}

类的实例化

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$h = new Hello();

类方法的引用

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$h->sayello();

类的构造器和外部形参

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class Man {
    /**
     * Man constructor.
     * @param int $age  年龄
     * @param string $name 名字
     */
    public function __construct($age, $name) {
    echo 'coustruct';
        $this->_age = $age;
        $this->_name = $name;
    }
    public function getAge() {
        return $this->_age;
    }
    public function getName() {
        return $this->_name;
    }
    private $_age, $_name;
}

类方法的声明和使用

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class Man {
    public static function sayHello() {
        echo 'Hello Men';
    }
}
Man::sayHello();

PHP静态属性的声明和使用：

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class Man {
    public function __construct($age, $name) {
    echo 'coustruct';
        $this->_age = $age;
        $this->_name = $name;
        Man::$NUM++;
        if (Man::$NUM>Man::MAX_NUM) {
            throw new Exception('不能创建更多的MAN');
        }
    }
    private $_age, $_name;
    private static $NUM = 0;
    const MAX_NUM = 100;
}
for ($i=0; $i<200; $i++) {
    $m = new Man($i,'Geek');
}

静态的属性和方法是为了描述类的信息，比如以上描述的就是初始人数是0，最大人数是100，成员属性和方法是为了描述类的实例。

类的继承

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class People {
   public function __construct($age, $name, $sex) {
       $this->_age = $age;
       $this->_name = $name;
       $this->_sex = $sex;
   }
   public function sayHi() {
       echo $this->_name.' say hi';
   }
   private $_age, $_name, $_sex;
}
class Women extends People {
   public function __construct($age, $name) {
       parent::__construct($age, $name, '女');
   }
}
$w = new Women(10, 'Geek');
$w->sayHi();

重写类方法

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class People {
   public function __construct($age, $name, $sex) {
       $this->_age = $age;
       $this->_name = $name;
       $this->_sex = $sex;
   }
   public function sayHi() {
       echo $this->_name.' say hi';
   }
   private $_age, $_name, $_sex;
}
class Women extends People {
   public function __construct($age, $name) {
       parent::__construct($age, $name, '女');
   }
   public function sayHi() {
       echo 'women '.$this->getName().' say hi';
   }
}
$w = new Women(10, 'Geek');
$w->sayHi();