Question

I have a language class with public data members:

class language {
    public $error = "There was an error";
}

Then I have many different classes that uses this class. How can I access this class from within other classes? You could of course instantiate an object of it inside all the classes that uses it, but I suppose that would drastically decrease the performance, if I were to do that with multiple classes.

I do only need one object, since I don’t change them anyway. So, I’ve done

$language = new language();

class name {
    private $language;

    public function __construct() {
        global $language;
        $this->language = $language;
    }


    public function method() {
        mysql_query(...) or die($this->language->error);
    }
}

Is this a good way to do it? Now I have to instantiate it in every “mother” script. And I suppose by doing __construct() I’m only passing a refrence, since I don’t use the clone word?

Answer 1

I do only need one object

This is the Singleton pattern.

Here is a quick example of a way to have only one instance of your Language class:

class Language {
  public $error = "text";

  private static $instance = null;

  public static function getInstance() {
    if (self::$instance == null)
      self::$instance = new self();
    return self::$instance;
  }

  private function __construct() {}
}

$lang = Language::getInstance();
$text = $lang->error;

You can also use dependency injection:

interface ILanguage {
  public function getError();
}

class Language implements ILanguage {
  private $error = "error";
  public function getError() {
    return $this->error;
  }
}

class name {
  private $language;

  public function __construct(ILanguage $lang) {
    $this->language = $lang;
  }

   public function method() {
     mysql_query(...) or die($this->language->getError());
   }
}

$language = new Language();
$n = new name($language);

This example of dependency injection is called constructor injection.