Question

我有__construct（$ parameter）

public function __construct($nick) {
    $query = "SELECT * FROM Users WHERE nick='".$nick."'";
    $result = App::runQuery($query);
    $user = $result->fetch_object();

    $this->id = $user->id;
    $this->nick = $user->nick;
    $this->email = $user->email;
    $this->password = $user->password;
    $this->birthDay = $user->birthDay;
    $this->sex = $user->sex;
    $this->about = $user->about;
    $this->city = $user->city;
    $this->photo = $user->photo;
    $this->following = $user->following;
    $this->followers = $user->followers;
    $this->statu = $user->statu; 

}

现在我想要一个没有这样参数的默认构造函数：

public function __construct() {

    $this->id = NULL;
    $this->nick = NULL;
    $this->email = NULL;
    $this->password = NULL;
    $this->birthDay = NULL;
    $this->sex = NULL;
    $this->about = NULL;
    $this->city = NULL;
    $this->photo = NULL;
    $this->following = NULL;
    $this->followers = NULL;
    $this->statu = NULL; 

}

但是出了点问题，我得到的错误是这样的：

Fatal error: Cannot redeclare User::__construct() in /Applications/MAMP/htdocs/xxx/Application/User.php on line 33

如何让两个带参数且没有参数的构造函数同时出现？

Answer 1

PHP中没有重载;你不能拥有相同名称但参数不同的方法

由于您的所有属性都默认为null，因此没有理由自行执行此操作。我建议做以下事情：

public function __construct($nick = null) {
    if ($nick != null) {
        $query = "SELECT * FROM Users WHERE nick='".$nick."'";
        $result = App::runQuery($query);
        $user = $result->fetch_object();

        $this->id = $user->id;
        $this->nick = $user->nick;
        $this->email = $user->email;
        $this->password = $user->password;
        $this->birthDay = $user->birthDay;
        $this->sex = $user->sex;
        $this->about = $user->about;
        $this->city = $user->city;
        $this->photo = $user->photo;
        $this->following = $user->following;
        $this->followers = $user->followers;
        $this->statu = $user->statu; 
    }
}

上述代码的替代方法是使用多个静态构造函数方法，并使用私有构造函数：

private function __construct() {
}

public static function createFromNick($nick) {
    $self = new self();

    $query = "SELECT * FROM Users WHERE nick='".$nick."'";
    $result = App::runQuery($query);
    $user = $result->fetch_object();

    $self->id = $user->id;
    $self->nick = $user->nick;
    $self->email = $user->email;
    $self->password = $user->password;
    $self->birthDay = $user->birthDay;
    $self->sex = $user->sex;
    $self->about = $user->about;
    $self->city = $user->city;
    $self->photo = $user->photo;
    $self->following = $user->following;
    $self->followers = $user->followers;
    $self->statu = $user->statu;

    return $self;
}

public static function createEmpty() {
    return new self();
}

Answer 2

public function __construct() {
    // allocate your stuff
}

public static function withRow( array $row ) {
    $instance = new self();
    $instance->fill( $row );
    return $instance;
}

protected function fill( array $row ) {
    // fill all properties from array
}

有关详细信息，请查看以下答案：Best way to do multiple constructors in PHP

Answer 3

非常感谢您的回答。我用自己的方式解决了这个问题。

public function __construct($nick) {
    if($nick != NULL) {//for user 
        $query = "SELECT * FROM Users WHERE nick='".$nick."'";
        $result = App::runQuery($query);
        $user = $result->fetch_object();

        $this->id = $user->id;
        $this->nick = $user->nick;
        $this->email = $user->email;
        $this->password = $user->password;
        $this->birthDay = $user->birthDay;
        $this->sex = $user->sex;
        $this->about = $user->about;
        $this->city = $user->city;
        $this->photo = $user->photo;
        $this->following = $user->following;
        $this->followers = $user->followers;
        $this->statu = $user->statu; 
    }else {//for null
        $this->id = NULL;
        $this->nick = NULL;
        $this->email = NULL;
        $this->password = NULL;
        $this->birthDay = NULL;
        $this->sex = NULL;
        $this->about = NULL;
        $this->city = NULL;
        $this->photo = NULL;
        $this->following = NULL;
        $this->followers = NULL;
        $this->statu = NULL;
    }

}

有效！

如何使用可选参数创建构造函数？

3 个答案: