Попробуйте PHP Dom :
$dom = new DomDocument;
$dom->loadHtml('
<span class=1>text here</span> TEXT I NEED TO GET <span class=2>more text</span>
');
$xpath = new DomXpath($dom);
foreach ($xpath->query('//body/text()') as $textNode) {
echo $textNode->nodeValue; // will be: ' TEXT I NEED TO GET '
}