<?php
$holder = <<< LOL
<p>some random text</p>
<div class="greybackground_desktop" style="background-color:#EFEFEF;">
<!-- /49527960/CSF_Article_Middle -->
<div style="padding-bottom:10px; padding-top: 10px; text-align:center;" id='div-gpt-ad-1441883689230-0'>
<script type='text/javascript'>
googletag.cmd.push(function() { googletag.display('div-gpt-ad-1441883689230-0'); });
</script>
</div>
</div>
<p>some more text</p>
<div><p>example of content that will be incorrectly removed</p></div>
<p>Text that follows</p>
LOL;
$result = preg_replace('%<div class="greybackground_desktop".*?</div>\s+</div>%si', '', $holder);
echo $result ;
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