How to add search by category in magento mini search

There is no free extension in magento commerce which will help you to search your store with particular category. I tried from myself and able to do, I am sharing my exprerience here with.

First create the drop down list of all category in form.mini.phtml

<select name="category" id="category_search_field">
<option value="">-- Any Category --</option>
<?php foreach ($catalog->getStoreCategories() as $_category): ?>
<?php if($_category->hasChildren()): ?>
<option class="parent-cat" value="<?php echo $_category->getId(); ?>"><?php echo $_category->getName();?></option>
<?php foreach ($_category->getChildren() as $subcategory):
if($subcategory->getIsActive()) : ?>
<option value="<?php echo $subcategory->getId(); ?>"<?php echo ($this->getRequest()->getQuery('category') == $subcategory->getId() ? ' selected="selected"': "") ?>><?php echo $subcategory->getName(); ?></option>
<?php endif; endforeach; ?>
<?php elseif($_category->getIsActive()): ?>
<option value="<?php echo $_category->getId(); ?>"><?php echo $_category->getName();?></option>
<?php endif; ?>
<?php endforeach ?>
</select>

Now go to app/code/core/Mage/CatalogSearch/Helper and open the Data.php and add the below code

public function getStoreCategories()
{
$helper = Mage::helper('catalog/category');
return $helper->getStoreCategories();
}
public function getSelectedCategory()
{
$catid = (int)addslashes($_REQUEST['category']);
$cat="";
if($catid>1)
$cat = Mage::getModel('catalog/category')->load($catid);
return $cat;
}

Now go to app/code/core/Mage/CatalogSearch/Model and open the Layer.php

replace

public function prepareProductCollection($collection)
{
$collection
->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
->addSearchFilter(Mage::helper('catalogsearch')->getQuery()->getQueryText())
->setStore(Mage::app()->getStore())
->addMinimalPrice()
->addFinalPrice()
->addTaxPercents()
->addStoreFilter()
->addUrlRewrite();
Mage::getSingleton('catalog/product_status')->addVisibleFilterToCollection($collection);
Mage::getSingleton('catalog/product_visibility')->addVisibleInSearchFilterToCollection($collection);
return $this;
}

with

public function prepareProductCollection($collection)
{
if(Mage::helper('catalogsearch')->getSelectedCategory()!="")
{
$collection
->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
->addSearchFilter(Mage::helper('catalogsearch')->getQuery()->getQueryText())
->setStore(Mage::app()->getStore())
->addMinimalPrice()
->addFinalPrice()
->addTaxPercents()
->addStoreFilter()
->addCategoryFilter(Mage::helper('catalogsearch')->getSelectedCategory())
->addUrlRewrite();
}
else
{
$collection
->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
->addSearchFilter(Mage::helper('catalogsearch')->getQuery()->getQueryText())
->setStore(Mage::app()->getStore())
->addMinimalPrice()
->addFinalPrice()
->addTaxPercents()
->addStoreFilter()
->addUrlRewrite();
}
Mage::getSingleton('catalog/product_status')->addVisibleFilterToCollection($collection);
Mage::getSingleton('catalog/product_visibility')->addVisibleInSearchFilterToCollection($collection);

return $this;
}

save and Enjoy.

cache is not generating in magento

Magento stores cache inside the cache folder which resides under Var folder of your root magento ,But if your cache folder or var folder have not correct file permisson that is 777 then magento will not be able to generate any cache. So change Var folder permission to 777 , you will see the effect.