Laravel4/PHP Model(or anything) extend multiple classes

We have some options:

Dependency Injection:

use ExternalClass;

class Model extends Eloquent {

    private $external;

    public function __construct(ExternalClass $external)
    {
        $this->external = $external;
    }

    public function doWhatever() 
    {
        return $this->external->do();
    }

    public function __call($name, $arguments)
    {
        return call_user_func_array(array($this->external,$name), $arguments);
    }
}

You don't have to pass a class to your model, Laravel will try to instantiate and inject that class for you.

edit

And you don't have to rewrite all methods, see this magic method __call? It will be fired automatically by PHP everytime a method is not found in your class, so you can use it to forward that call to your external class.

end-edit

Traits: (this is PHP 5.4+)

class Model extends Eloquent {

    use MyTraits;

    public function doWhatever() 
    {
        return $this->do();
    }
}

trait MyTraits {

    public function do()
    {
        /// this metho will be available in your class 
    }

}

You can also use the Repository Pattern:

class DataRepository {

    private $user;

    private $external;

    public function __construct(User $user, ExternalClass $external)
    {
        $this->user = $user;

        $this->external = $external;
    }

    public function allUsers() 
    {
        return $this->user->all();
    }

    public function doWhatever() 
    {
        return $this->external->do($this->user);
    }
}

There some others, but your project is what will really tell you what's best.

EDIT

Note that you have to be aware of the __call magic method, because Laravel also uses it to deliver dynamic methods, like whereColumnname() and you risk breaking by using it. But this is also something you can circumvent with a little more code:

public function __call($name, $arguments)
{
    // If the method is not one of your package ones, try execute an Eloquent (parent) one

    if ( ! in_array($name, ['methodA', 'methodB', 'methodC']))
    {
        return parent::__call($name, $arguments);
    }
    else
    {
        return call_user_func_array(array($this->external,$name), $arguments);
    }
}