How to get products from categories in magento?

[Kaushal Elsner]

I want to display all the products from the individual categories. I am putting my code here that what i have done so far.

<?php
    $_main_categories = $this->getStoreCategories();
 
    foreach ($_main_categories as $_main_category):
?>
        <li>
            <div style="width:593px;">
            <?php
                $_products = $_main_category->getProductCollection();
                $i=0;
                foreach ($_products->getItems() as $_product):
                    if($i<3)
                    {
            ?>
                        <img src="<?php echo $this->helper('catalog/image')->init($_product, 'small_image')->resize(80) ?>" />
            <?php
                    }
                $i++;
                endforeach
            ?>
            </div>
 
            <div class="lof-main-item-desc">
                <h3><?php echo $_main_category->getName(); ?></h3>
                <p>The one thing about a Web site, it always changes! Joomla! makes it easy to add Articles, content,...</p>
            </div>
        </li>
<?php
    endforeach
?>
 

I want to display product images only but it is giving me error like -
Fatal error: Call to a member function getItems() on a non-object in C:\xampp\htdocs\xampp\Kaushal\r4power\app\design\f rontend\default\r4power\template\catalog\navigatio n\slider_horizontal_nav.phtml on line 11.