[PHP] Re: Referencing Containing (Non-Parent) Object?

[Bogdan Ribic]

Morgan Doocy wrote:

I'm trying to figure out if PHP has the facility to reference containing, 
non-parent objects. I have three classes, embedded hierarchically, but which 
are NOT extended classes of their containing objects. I'd like to be able to 
reference variables in the higher-level objects from the lower-level objects.
To illustrate:

<?php

class Country {
        var $name;
        var $states;
        
        function Country($name = '', $states = array()) {
                $this->name = $name;
                $this->states = $states;
        }
}

class State {
        var $name;
        var $cities;
        
        function State($name = '', $cities = array()) {
                $this->name = $name;
                $this->cities = $cities;
        }
}

class City {
        var $name;
        
        fuction City($name = '') {
                $this->name = '';
        }
        
        function name_with_state() {
                return "$this->name, " . /* parent node reference */->name;
        }
}

$countries = array (
        'USA' => new Country('United States',
                array (
                        'WA' => new State('Washington',
                                array (
                                        'SEA' => new City('Seattle'),
                                        'GEG' => new City('Spokane')
                                )
                        ),
                        'CA' => new State('California',
                                array (
                                        'LAX' => new City('Los Angeles'),
                                        'SFO' => new City('San Francisco')
                                )
                        )
                )
        )
);

echo $countries['USA']->states['WA']->cities['SEA']->name_with_state();
// Output: 'Seattle, Washington'

?>

Obviously, just extending Country doesn't make sense: a State isn't a type of 
Country, and a City isn't a type of State -- but States are part of Countries, 
and Cities are part of States. Plus, if City was just an extended State (which 
in turn is an extended Country), it would contain both a $states and a $cities 
variable. Which doesn't make sense.

What, if anything, do I replace /* parent node reference */ with in 
City::name_with_state()?

Thanks,

Morgan


I suspect you want the functionality of Java embedded clases, where 
embedded class can access fields of its container. If that's what you 
mean, then sorry, PHP doesn't have that. You would have to keep a 
reference ro parent object as a variable in child object, ie your City 
should have a var $_state variable, etc.


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