trying to sort discounted products in a Magento .phtml block, adding any function disables the block

Question

I am trying to create a block which shows the 5 top selling products, 5 most viewed products and 5 largest discounted products on a Magento 1.7.0.2 site.

The block is defined as follows in local.xml:

<reference name="content">
   <block type="core/template" name="movies_block" template="catalog/product-block.phtml" before="-">
      <action method="setData"><name>category_id</name><value>5</value></action>
   </block>
</reference>

(you pass it a category id, the idea being it can be quickly reused throughout my theme for categories of my choosing)

I have written and tested code for displaying top sellers and most viewed, but I'm struggling with a way to efficiently sort the top 5 most discounted. I'm defining a discount as the % difference between 'price' and 'special_price'.

My code for this is as follows:

$visibility = array(
   Mage_Catalog_Model_Product_Visibility::VISIBILITY_BOTH,
   Mage_Catalog_Model_Product_Visibility::VISIBILITY_IN_CATALOG
);

$catNum = $this->getCategoryId(); // grab cat id from xml
$category = Mage::getModel('catalog/category')->load($catNum);

// load products from $category
$_productCollection = Mage::getResourceModel('catalog/product_collection')
                          ->addAttributeToSelect('*')
                          ->addAttributeToFilter('visibility', $visibility)
                          ->addCategoryFilter($category);

$saleProducts = array();        
$i=0;                                           
foreach($_productCollection as $product): 
   if($product->getSpecialPrice()): // if a product has a special price
      /* calculate discount as percentage and add it to $product array of each */
      $product['discount'] = $product->getSpecialPrice()/$product->getPrice()*100;
      $saleProducts[$i] = $product; // put discounted products into separate array
      $i++;
   endif;
endforeach;

This leaves an array $saleProducts, of products which have a 'special_price'. However, I want just the top 5 most discounted (highest value in $product['discount'] first).

I've been attempting to sort the array using:

function cmp($a, $b) {
   return ($a['discount'] - $b['discount']);
}

usort($saleProducts, "cmp");

But as soon as I add anything to my code with 'function' in it, the whole block no longer displays... happens even if I just write:

function sortByDiscount($a, $b) {};

anywhere in the .phtml file, is Magento preventing me from creating a function? Anybody else tackled this particular problem? I have a feeling my way might be quite slow, especially since I used other product collections with filters earlier on in the same .phtml file, and this block needs to work with categories of up to 20,000 products.

Any suggestions welcome.

Answer 1

Anonymous functions are supported from PHP 5.3 on so you won't be able to use them.

As far as I know phtml file is included into it's block class so you can't write a new function in a phtml file. You will have to extend the block class or create a new helper class and then call

usort( $saleProducts, array('foo', 'bar'));

where foo is your class name and bar is the function name (and the comparator function should be static).

Answer 2

http://php.net/manual/en/functions.anonymous.php

Anonymous functions supported only from PHP 5.3. Rewrite your usort method to be like:

usort($saleProducts, array($this, 'cmp'));

So, you will move your code to block and call its method.