Modifying existing class

[Grayda]

In my latest PHP project, I have a few classes that perform various things, for example, authenticating users, pulling information from databases and so forth. One of the big points of my project is allowing trusted users to eval() code, so they can integrate existing PHP code into their website. What I would like, is for trusted users to be able to "overwrite" parts of the code at run-time. For example, if this is my security class:

 

<?php class Security {

...

function authenticateUser($user, $password) {
    // Code to authenticate user goes here
}

...

} ?>

 

I would like users to be able to do write something like this:

 

<?php 

class Security {

...

function authenticateUsers($user, $password) {
   // A different authentication scheme in here
}

...

} ?>

 

Much like "class NewSecurity extends Security", but instead of creating an extended class, merely re-defining / re-using existing methods in an existing class

 

I suppose this is more of a personal curiosity thing rather than a serious idea for my application (although, releasing patches without editing real files on the server, has it's advantages ), but the question is, can it be done?

[ignace]

your problem can be solved using the abstract factory pattern

 

abstract class Security
{
    abstract public function authenticateUser($username, $password);
    
    public static function factory($username, $password, $auth)
    {
        if ($auth == "http") {
            $class = new HttpAuth();
            /**
             * this is why you need it to be an abstract factory, so you can be sure that the class will have a authenticateUser() method
             * in addition you can do, after initiation: if (is_a($class, 'Security')) to be sure the class will have a authenticateUser() method
             */
            $class->authenticateUser($username, $password);
        }
        ...
    }
}

class HttpAuth extends Security
{
   public function authenticateUser($username, $password) {/* authentication method 1 */}
}

class FormAuth extends Security
{
   public function authenticateUser($username, $password) {/* authentication method 2 */}
}

 

in your script then:

 

$authentication_method =  ...
Security::factory($username, $password, $authentication_method); // depending on $authentication_method HttpAuth or FormAuth will be initiated

[Grayda]

Thanks for the help ignace, but I'm still a little confused. Can I have:

 

<?php

// This is in base.php which is a file on my web-server
abstract class Person {
abstract public function getRealName($username);
}

?>

 

and

 

<?php

// This is code that a user copies and pastes into the online editor. This page is stored within a DATABASE so it needs to be eval()'d when it's grabbed from the database and the user is authenticated

class Person {

function getRealName($username) {
echo "Hi, your real name is: " . $someclass->somefunction;
}

}

?>

 

or do I still need to extend classes? Also, what about a default implementation? Could I have something like (and remember that this is pseudo-code and I don't know if this can or cannot be done):

 

<?php

// This goes into base.php which is located in a directory on the webserver

abstract class Person {
abstract public function getRealName($username) {
echo "Hi, your real name is: " . $someOtherClass->someOtherFunction($username);
}
}

?>

 

and:

 

<?php

// This is what gets copied and pasted into the database, so it must be eval()'d
class Person {

function getRealName($username) {
return $someOtherClass->someOtherFunction($username);
}

}

?>

 

So that way if no overwriting is done, it will use the default method, but if one is specified, it'll use that?

 

I've seen Runkit for PHP (http://au2.php.net/manual/en/intro.runkit.php), which lets you do this, but it also provides extra stuff which I might not need, which is why I wondered if there was a native way to do this in PHP5

 

I hope this makes sense, and thanks for taking the time to help out