I have started to learn magento and I have some doubts about how it works, could someone help me with it or can suggest some tutorial from where I can learn more about magento. In

/app/design/frontend/../../template/catalog/product/widget/new/content/new_grid.phtml

file there is a piece of code

$this->getProductCollection()

I know this function can be found in

/app/code/core/Mage/Catalog/Block/Product/Widget/New.php

But there is no such function, I also looked in the parent class and there also I could not find this function.

I found another function in

/app/code/core/Mage/Catalog/Block/Product/Widget/New.php

Below is the function

protected function _getProductCollection()
{
    switch ($this->getDisplayType()) {
        case self::DISPLAY_TYPE_NEW_PRODUCTS:
            $collection = parent::_getProductCollection();
            break;
        default:
            $collection = $this->_getRecentlyAddedProductsCollection();
            break;
    }
    return $collection;
}

and I know this function is called but my question is why and how? These two have different names then how they can be same. Do it means that "_" is only used if a function is protected and it does not have to do anything with the function name.

And also when I echoed

$this->getDisplayType()

then I got 'new_products' but if you see in this function then magento is using self::DISPLAY_TYPE_NEW_PRODUCTS in case then how these two cases or strings are similar.

Also please explain this line

parent::_getProductCollection()

do it means call _getProductCollection() from parent class and if yes then where this is specified in magento.

I am learning magento and I have some doubts about how it works, could someone help me with it or can suggest some tutorial from where I can learn more about magento. In

/app/design/frontend/../../template/catalog/product/widget/new/content/new_grid.phtml

file there is a piece of code

$this->getProductCollection()

I know this function can be found in

/app/code/core/Mage/Catalog/Block/Product/Widget/New.php

But there is no such function, I also looked in the parent class and there also I could not find this function.

I found another function in

/app/code/core/Mage/Catalog/Block/Product/Widget/New.php

Below is the function

protected function _getProductCollection()
{
    switch ($this->getDisplayType()) {
        case self::DISPLAY_TYPE_NEW_PRODUCTS:
            $collection = parent::_getProductCollection();
            break;
        default:
            $collection = $this->_getRecentlyAddedProductsCollection();
            break;
    }
    return $collection;
}

and I know this function is called but my question is why and how? These two have different names then how they can be same. Do it means that "_" is only used if a function is protected and it does not have to do anything with the function name.

And also when I echoed

$this->getDisplayType()

then I got 'new_products' but if you see in this function then magento is using self::DISPLAY_TYPE_NEW_PRODUCTS in case then how these two cases or strings are similar.

Also please explain this line

parent::_getProductCollection()

do it means call _getProductCollection() from parent class and if yes then where this is specified in magento.