PHP对象继承的麻烦

Question

I am building a page through a series of include files. Many (not all) of the include files are classes of various things that I need stored as objects. For instance, one of my pages is:

 class site {
     var $siteid;
     var $sitename;

     function __construct($id, $name) {
        $this->siteid = $id;
        $this->sitename = $name;
     }

     function get_siteid(){
        return $this->sitename;
 }

and then on another page I have:

$site = new site("4","My Site");

So, on a subsequent include page I create another class called "page". While creating this class I need to reference the siteid value instantiated previously for $site, but I can't seem to get at it.

I've tried $site->get_siteid() but I get a message that says "undefined variable."

Strangely, on a regular HTML page later on, I am able to get the site id simply with $site->siteid, but from what I have read this is not a good practice, and this also doesn't work within the page class anyway.

I'm still pretty new to OO coding and so I am sure I am missing something pretty basic here, but have tried a lot of things and cannot seem to make it work.

Thanks in advance. :)

Answer 1

Firstly, since you're using PHP5, use access specifiers when declaring properties and methods:

Change:

var $siteid;
var $sitename;

To:

public $siteid;
public $sitename;

Or make them private or protected if preferred. See the manual for more info on visibility.

I've tried $site->get_site(id) but I get a message that says "undefined variable."

There is no method called get_site . There is one called get_siteid but it inexplicably returns the site name. You'll want to straighten that out.

I am able to get the site id simply with $site->siteid, but from what I have read this is not a good practice

There's no point in making getters/setters that simply return/set member variables. Just declare the member public and access it directly. Nothing wrong with that.

Answer 2

HTTP is a connectionless protocol. So state based information is not saved between requests. The object that is instantiated (eg. $site) will not be maintained between pages.

If you have persistent data that you need to store objects you can serialize the objects and store it in a mysql table or a file. Then you can retrieve the serialized object by a using a key and the deserialize it and use it.

Answer 3

Several things

1. Intentionally or not, you have a typo. Your method is named get_siteid() but you reference $site->get_site(id)
2. id is not a valid variable, you should be using $id
3. You're method doesn't receive a parameter but you're sending one
4. The reason $site->siteid works is because site::$siteid is public. To prevent this, make the variable protected or private .