Question

I’ve got a number of product classes which extend a parent product class. Each of these implements its own version of a PRODUCT_ID const. A method in a customer object will pull the PRODUCT_ID ‘s from the DB. I’d then like to instanciate the relevant product object and add it to an array.

Any ideas how I can dynamically find out which product object has the specific PRODUCT_ID const?

Sorry if that is a bit confusing!

Answer 1

The only way to do this would be to first loop through all of the declared classes, then check if they’re a subclass of the parent product and finally to check if the PRODUCT_ID constant is defined and equal to the product you’re looking for.

Here an example:

<?php

class Product
{
}

class Stack extends Product
{
  const PRODUCT_ID = 1;
}

class Overflow extends Product
{
  const PRODUCT_ID = 2;
}

function getSubclasses($parentClassName)
{
    $classes = array();
    foreach (get_declared_classes() as $className)
    {
        if (is_subclass_of($className, $parentClassName))
            $classes[] = $className;
    }

    return $classes;
}

function find_product($product_id)
{
  foreach ( get_declared_classes() as $class )
    if ( is_subclass_of($class, 'Product') )
      if ( constant($class . '::PRODUCT_ID') == $product_id )
        return $class;
}

echo find_product(1); // Outputs "Stack"