Caches category data for Opencart 1.5 to make it faster. Opencart installs with alot of categories are really slow. http://forum.opencart.com/viewtopic.php?f=161&t=126241 here is a new version for Opencart 3.0: https://gist.github.com/weismannweb/8add8fab5be99854db5c618d751281b2

cache_category_data.xml

<modification>

    <id>Cache category data to speed up page load for store with many categories and sub categories.</id>
    <version>1.0.1</version>
    <vqmver>2.3.2</vqmver>
    <author>Weismann Web - www.weismannweb.com</author>

    <file name="catalog/controller/module/category.php">
        <operation>
            <search position="after"><![CDATA[
            foreach ($categories as $category) {
            ]]></search>
            <add><![CDATA[
						$category_data = $this->cache->get('vqmod_category_data_controller_module_category'.$this->config->get('config_store_id'));
	
		    if ($category_data) {
		        $this->data['categories'] = $category_data;
			    break;
		    }
            ]]></add>
        </operation>
        <operation>
            <search position="before"><![CDATA[
            if (file_exists(DIR_TEMPLATE . $this->config->get('config_template') . '/template/module/category.tpl')) {
            ]]></search>
            <add><![CDATA[
            if (!$category_data) {
			$this->cache->set('vqmod_category_data_controller_module_category'.$this->config->get('config_store_id'), $this->data['categories']);
			}
            ]]></add>
        </operation>
    </file>

 <file name="catalog/controller/common/header.php">
        <operation>
            <search position="after"><![CDATA[
            foreach ($categories as $category) {
            ]]></search>
            <add><![CDATA[
            $category_data = $this->cache->get('vqmod_category_data_controller_common_header'.$this->config->get('config_store_id'));
	
		    if ($category_data) {
		        $this->data['categories'] = $category_data;
			    break;
		    }
            ]]></add>
        </operation>
        <operation>
            <search position="before"><![CDATA[
            $this->children = array(
            ]]></search>
            <add><![CDATA[
            if (!$category_data) {
			$this->cache->set('vqmod_category_data_controller_common_header'.$this->config->get('config_store_id'), $this->data['categories']);
			}
            ]]></add>
        </operation>
    </file>

 
</modification>

<!--
<modification>  - This is the highest level of the file and there can only be one
<id>            - This is the name of the mod. Format: Free form text. (Informational)
<version>       - This is the version of the mod. Format: Number and Decimal (1.0.0) (Informational)
<author>        - This is the author of the mod. Format: Free form text (Informational)
<file>          - This is the name of the file to modify. Requires attribute "name" as relative filename (catalog/controller/product/product.php). There can be multiple
<operation>     - This is the wrapper of the actual operation occuring. There can be multiple operations to the same file.
<search>        - This is the first required step of the operation. Uses an optional attribute "position" set to before|after|replace. replace is default. One per operation. Use CDATA tags to wrap code.
<add>           - This is the second required step of the operation. Uses an optional attribute "trim" set to true|false to trim away whitespace and linebreaks. false is default. One per operation. Location of added data depends on the position of the <search> command. Use CDATA tags to wrap code.
<![CDATA[  ]]>  - These are called CDATA tags and they are used by xml to specify that the data between should not be evaluated.
-->

Thanks for this. Could you tell me how can I apply this to my opencart store?

for oc 2 ? please help me