<p>Fired inside the <code>\XF\Service\User\MergeService</code> class in the <code>combineData()</code> method.</p>

<p>This allows you to add extra fields whose values should be combined while doing a user merge.</p>

<p>Callback signature:</p>
<blockquote><code><em>\XF\Entity\User</em> $target, <em>\XF\Entity\User</em> $source, <em>\XF\Service\User\MergeService</em> $mergeService</code></blockquote>

<p>Arguments:</p>
<ol>
	<li><code><em>\XF\Entity\User</em> $target</code> - The target user (the user being merged into).</li>
	<li><code><em>\XF\Entity\User</em> $source</code> - The source user (the user being merged from). This user will be deleted at the end of the process.</li>
	<li><code><em>\XF\Service\User\MergeService</em> $mergeService</code> - The service being used to do the merge.</li>
</ol>