"/(?:целое слово)/"

	$in = array(
'page1:
<div id="head">
<div>
<div class="phone">(347) 100-200<br></div>
</div>
</div>'
,
'page2:
<div id="head">
<div>
<div class="second_phone"> 2-300-300</div>
</div>
</div>'
,
'page3:
<div id="head">
<div class="my_mob"> 2-300300</div>
</div>'
	);

	foreach ($in as $v) {
		$doc = new DOMDocument();
		$doc->loadHTML($v);
		foreach ($doc->getElementsByTagName('div') as $div) {
			foreach ($div->childNodes as $child) {
				if ($child->hasChildNodes() && $child->hasAttributes())
					echo trim($child->textContent), PHP_EOL;
			}
		}
	}
?>