Magento Check if a module is installed, enabled or active.

$moduleName = 'Mage_Core'; // edit to your required module name
if (Mage::helper('core')->isModuleEnabled($moduleName)) {
    echo "Module is enabled.";
} else {
    echo "Module is disabled.";
}

Magento How to get product stock quantity & other stock information?

1. Load product by product ID
$id = 52;
$_product = Mage::getModel('catalog/product')->load($id);

2. Load product by SKU
$sku = "microsoftnatural";
$_product = Mage::getModel('catalog/product')->loadByAttribute('sku', $sku);

Now, get stock information for the loaded product.
$stock = Mage::getModel('cataloginventory/stock_item')->loadByProduct($_product);

You can check stock data in this way:-
echo "<pre>"; print_r($stock->getData()); echo "</pre>";

Or, you can print individually like this:-
echo $stock->getQty();
echo $stock->getMinQty();
echo $stock->getMinSaleQty();

Magento How to get all associated children product of a configurable product?

Load product by product id

$product = Mage::getModel('catalog/product')
                    ->load(YOUR_PRODUCT_ID);
 
Get children products (all associated children products data)

$childProducts = Mage::getModel('catalog/product_type_configurable')
                ->getUsedProducts(null,$product);

Magento Load product of specific store.

$storeId = Mage::app()->getStore()->getId();

$product = Mage::getModel('catalog/product')
            ->setStoreId($storeId)
            ->load($key);

Magento Load multiple products at once.

Following are load product useing ids.

$productIds = array(5, 22, 45, 75, 88);

$productIds = array(5, 22, 45, 75, 88);
$attributes = Mage::getSingleton('catalog/config')->getProductAttributes();
$collection = Mage::getModel('catalog/product')
                ->getCollection()              
                ->addAttributeToFilter('entity_id', array('in' => $productIds))
                ->addAttributeToSelect($attributes);
               
Following are load product useing SKUs.

$productSku = array('1111', '1112', '1113', 'HTC Touch Diamond', 'microsoftnatural');
$attributes = Mage::getSingleton('catalog/config')->getProductAttributes();
$collection = Mage::getModel('catalog/product')
                ->getCollection()              
                ->addAttributeToFilter('sku', array('in' => $productSku))
                ->addAttributeToSelect($attributes);
               

Hope it helps. Thanks.

Magento validator for configuration text field

Add following class in your system.xml. review following image.

Magento Category Accordian with Alphabatically sorting.

Add following code in any PHTML file and call in left/right side.

<div class="block block-left-nav" id="sidebox">
    <div class="block-title">
        <strong><span><?php echo $this->__('categories') ?></span></strong>
    </div>
    <div class="block-content">
        <ul id="nav-left">
            <?php
            $collection = Mage::getModel('catalog/category')->getCollection()
                    ->addAttributeToSelect('*')
                    ->addAttributeToSelect('is_active')
                    ->addAttributeToSort('name', 'ASC');
            foreach ($collection as $_category1):
                if ($this->getRequest()->getModuleName() == 'vendor') {
                    $_category = Mage::getModel('catalog/category')->load($_category1['entity_id']);
                    ?>
                    <?php if ($_category->getIsActive() && $_category1['entity_id'] != 2 && $_category->getLevel() == 2) { ?>
                        <?php $potential = $_category->hasChildren(); ?>
                        <li><a id="block-title" class="<?php echo ($open) ? 'active' : 'inactive' ?>" href="<?php
                            if ($potential) {
                                echo $this->getCategoryUrl($_category);
                                //echo 'javascript:void(0)';
                            } else {
                                echo $this->getCategoryUrl($_category);
                            }
                            ?> "><?php echo $_category->getName(); ?></a>
                               <?php if ($potential) { ?>
                                <ul class="top-level">
                                    <?php
                                    $_cat_level_2 = array();
                                    foreach ($_category->getChildrenCategories() as $_category2) {
                                        $_cat_level_2[$_category2->getName()] = $_category2;
                                    }
                                    ksort($_cat_level_2);
                                    ?>
                                    <?php foreach ($_cat_level_2 as $subcategory): ?>
                                        <li class="second-category">
                                            <a  class="<?php echo ($open) ? 'active' : '' ?>" href="<?php echo $this->getCategoryUrl($subcategory); ?>"><?php echo $subcategory->getName(); ?></a>
                                            <?php if ($potential) { ?>
                                                <ul class="sub-level">
                                                    <?php
                                                    $_cat_level_3 = array();
                                                    foreach ($subcategory->getChildrenCategories() as $_category3) {
                                                        $_cat_level_3[$_category3->getName()] = $_category3;
                                                    }
                                                    ksort($_cat_level_3);
                                                    ?>
                                                    <?php foreach ($_cat_level_3 as $subsubcategory): ?>
                                                        <li><a class="<?php echo ($open) ? 'active' : '' ?>" href="<?php echo $this->getCategoryUrl($subsubcategory); ?>"><?php echo $subsubcategory->getName(); ?></a></li>
                                                    <?php endforeach; ?>
                                                </ul>
                                            <?php } ?>  
                                        </li>
                                    <?php endforeach; ?>
                                </ul>
                            <?php } ?>
                        </li>
                        <?php
                    }
                }
                else {
                    $_category = Mage::getModel('catalog/category')->load($_category1['entity_id']);
                    ?>
                    <?php if ($_category->getIsActive() && $_category1['entity_id'] != 2 && $_category->getLevel() == 2) { ?>
                        <?php
                        $open = $this->isCategoryActive($_category);
                        if (Mage::registry('current_category')->getid() == $_category1['entity_id']) {
                            $open = 'yes';
                        }
                        ?>
                        <?php $potential = $_category->hasChildren(); ?>
                        <li><a id="block-title" class="<?php echo ($open) ? 'active' : 'inactive' ?>" href="<?php
                            if ($open) {
                                echo $this->getCategoryUrl($_category);
                            } elseif ($potential) {
                                //echo 'javascript:void(0)';
                                echo $this->getCategoryUrl($_category);
                            } else {
                                echo $this->getCategoryUrl($_category);
                            }
                            ?> "><?php echo $_category->getName(); ?></a>
                               <?php if ($potential) { ?>
                                   <?php
                                   $_cat_level_2 = array();
                                   foreach ($_category->getChildrenCategories() as $_category2) {
                                       $_cat_level_2[$_category2->getName()] = $_category2;
                                   }
                                   ksort($_cat_level_2);
                                   ?>
                                <ul class="top-level">
                                    <?php foreach ($_cat_level_2 as $subcategory): ?>
                                        <?php
                                        $open = $this->isCategoryActive($subcategory);
                                        if (Mage::registry('current_category')->getid() == $subcategory->getId()) {
                                            $open = 'yes';
                                        }
                                        ?>
                    <?php $potential = $subcategory->hasChildren(); ?>
                                        <li class="second-category">
                                            <a  class="<?php echo ($open) ? 'active' : '' ?>" href="<?php echo $this->getCategoryUrl($subcategory); ?>"><?php echo $subcategory->getName(); ?></a>
                                                <?php if ($potential) { ?>
                                                <ul class="sub-level">
                                                    <?php
                                                    $_cat_level_3 = array();
                                                    foreach ($subcategory->getChildrenCategories() as $_category3) {
                                                        $_cat_level_3[$_category3->getName()] = $_category3;
                                                    }
                                                    ksort($_cat_level_3);
                                                    ?>
                                                    <?php foreach ($_cat_level_3 as $subsubcategory): ?>
                                                        <?php
                                                        $open = $this->isCategoryActive($subsubcategory);
                                                        if (Mage::registry('current_category')->getid() == $subsubcategory->getId()) {
                                                            $open = 'yes';
                                                        }
                                                        ?>
                                                        <li><a class="<?php echo ($open) ? 'active' : '' ?>" href="<?php echo $this->getCategoryUrl($subsubcategory); ?>"><?php echo $subsubcategory->getName(); ?></a></li>
                                                <?php endforeach; ?>
                                                </ul>
                                        <?php } ?>  
                                        </li>
                                <?php endforeach; ?>
                                </ul>
                        <?php } ?>
                        </li>
                    <?php }
                }
                ?>
<?php endforeach; ?>
        </ul>
    </div>
</div>