How to create constructor with optional parameters? [duplicate]

Question

I have __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; 

}

And now I want to have a default constructor without parameters like this:

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; 

}

But something is wrong and I get error like this:

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

How can I have two constructors with parameters and without parameters at the same time?

Answer 1

1. There is no overloading in PHP; you cannot have methods with the same names but different parameters

2. Since all of your properties will default to null, there's no reason to do it yourself. I would suggest doing the following:

   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; 
       }
   }
   

3. An alternative to the above code is to have multiple, static constructor methods, and use a private constructor:

   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();
   }