This article for those who wants integrate Emerald into core of their Joomla extensions programmatically.

Let’s assume you have categories and you want to restrict those. You can add parameters to category edit form, where administrator will select subscription plan and some other options.

Then in your code, before you display that category, you use those parameters to check if this category is restricted. And if yes - check if user has a subscription through Emerald API.

Step 1: Prepare restriction parameter.

How you can easily show parameters. I hope you use native Joomla form manager and user XML file to form list of form elements.

First you have to add attribute to <fieldset> or <fields> element.

<fieldset addfieldpath="/components/com_emerald/models/fields/">

This attribute tells where to look for special form elements type we will use.

	<fieldset name="emerald" label="Emerald Integration" addfieldpath="/components/com_emerald/models/fields/">
		<field name="plans" type="planslist" multiple="multiple" class="inputbox" label="Select plans" />
		<field name="count_limit" type="radio" class="btn-group" default="0" label="Count usages">
			<option value="0">CNO</option>
			<option value="1">CYES</option>
		</field>
		<field name="plans_msg" type="text" size="40" label="Restriction message" rows="6" cols="30"
			default="Only our paid members can access this." />
	</fieldset>

Fist parameter of type planslist will show list of the plans. One important attribute is multiple. If you what to allow select multiple plans set it true.

Count usages option allow you to integrate special Emerald feature to limit not only by time but only by number of times subscription should be used.

Step 2: Protection

To check if this category is protected you simple check if plans was selected in parameters. The code will looks most of all like this.

if($category->params->get('plans')) 
{
	// check for restriction
}

Or may be like this

if($category->plans) 
{
	// check for restriction
}

This depends on how you will store parameters. As JSON encoded string or in a separate fields.

Now lets check access.

$api = JPATH_ROOT./components/com_emerald/api.php';
if(JFile::exists($api))
{
	require_once $api;
	if(!EmeraldApi::hasSubscription($plans, $msg, $user_id, $count, $redirect, $url))
	{
		return;
	}
}

First you have to check if api.php file exists to avoid fatal errors.

To check user subscriptions you will use EmeraldApi::hasSubscription(). This function return true or false or automatically redirect to list of the plans to purchase if false. This mean that is $redirect parameter is true you do not need IF statement. You can use it like this.

$api = JPATH_ROOT./components/com_emerald/api.php';
if(JFile::exists($api))
{
	require_once $api;
	EmeraldApi::hasSubscription($plans, $msg, $user_id, $count, TRUE, $url);
}

Then you know that if there is no subscription user will be redirected. Or use $redirect equal to false if you what to manage behavior manually.