<p>Called before a set of activity summary emails are sent.</p>

<p>This can be used to set global display values to be displayed at the top of the activity summary email.</p>

<p>Global display values are useful for displaying stats that are relevant to all users, such as the number of users who have registered recently.</p>

<p>Callback signature:</p>
<blockquote><code><em>array</em> &amp;$globalDisplayValues</code></blockquote>

<p>Arguments:</p>
<ol>
	<li><code><em>array</em> &amp;$globalDisplayValues</code> - an array containing global display values.</li>
</ol>

<p>Example:</p>
<pre>public static function activitySummaryInstanceDisplayValues(\XF\ActivitySummary\Instance $instance)
{
	$globalDisplayValues[] = [
		'label' => 'some_value', // can be phrase title or phrase object
		'value' => 1000 // value to display
	];
}</pre>