## 一、概述 php通過class關鍵字聲明類，其中一個類包含屬性和方法兩部分；某類事物的實例，比如人類指類，那單個人就是對象。 ``` class Person { # 屬性 private $name = "cercy"; public $sex = "girl"; protected $height = 1.88; # 方法 public function setName($name){ $this->name = $name; } public function getName(){ return $this->name; } } # 實例化一個對象 $myObject = new Person(); echo $myObject->name; echo $myObject->getName(); ``` ## 二、構造函數 類中存在默認的構造函數，也可以指定構造函數，用于在實例化對象時指定屬性而不是使用默認的屬性，構造函數自動執行，無需手動調用。 ``` class Person { private $name = "jimson"; public $sex = "boy"; public function getName(){ return $this->$name; } public function __construct($name,$sex){ $this->$name = $name; $this->$sex = $sex; } } $newObj = new Person("Tim","girl"); ``` ## 三、析構函數 也是自動執行的函數，用于實例化對象之后將類銷毀。 ``` class Person { # …… public function __destruct(){ echo __CLASS__."被銷毀了"; } } $newObj = new Person("Tim","girl"); ``` ## 四、繼承 可以通過關鍵字extends來定義類，被繼承的類叫父類，以此繼承父類的非private屬性和方法。 ``` class Person { private $name = "jimson"; public $sex = "boy"; public function getName(){ return $this->$name; } public function __construct($name,$sex){ $this->$name = $name; $this->$sex = $sex; } } class Teacher extends Person{ public $salary = "3000"; public function teachStudent(){ echo "傳授學生知識"; } } $teacher = new Teacher("james","boy"); # 調用父類的方法 $teacher->getName(); # 調用自己的方法 $teacher->teachStudent(); ``` 子類也可以用自己的構造函數，同時調用父類的構造函數。 ``` class Person { private $name = "jimson"; public $sex = "boy"; public function getName(){ return $name; } public function __construct($name,$sex){ $this->$name = $name; $this->$sex = $sex; } } class Teacher extends Person{ public $salary = "3000"; public function getSalary(){ return $this->$salary; } public function __construct($name,$sex,$salary){ # 調用父類的構造函數 parent::__construct($name,$sex); $this->$salary = $salary; } } $teacher = new Teacher("james","boy","10000"); echo $teacher->getName(); //james echo $teacher->getSalary(); //10000 ```