如何使用可选参数创建构造函数？

我已经__construct（$参数）如何使用可选参数创建构造函数？

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; 

}

现在我想有这样的无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; 

}

但什么是错的，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

我怎样才能有两个参数和不带参数的构造函数在同一时间？

来源

2015-02-08 Mehmet

虽然你可能在这两年后没有工作，但你在这段代码中有一个明显的SQL注入漏洞 – Casey 2017-07-27 19:23:41

非常感谢您的回答。我用我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; 
    } 

}

它的工作原理！

来源

2015-02-08 16:48:52 Mehmet

PHP中没有重载;你不能拥有同名但参数不同的方法

由于你所有的属性默认为null，所以没有理由自己去做。我建议做如下：

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有多重，静态构造方法，并使用私有构造：

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(); 
}

来源

2015-02-08 15:43:08

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 
}

对于详细检查答案：Best way to do multiple constructors in PHP

来源

2015-02-08 15:50:17

如何使用可选参数创建构造函数？

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