<?php
include("simple_html_dom.php");
$html = "<a id='tag1'>A</a>
         <a id='tag2'>B</a>
         <a id='tag3'>C</a>
        ";

$dom = str_get_html($html);
$select = NULL;
foreach($dom->find('a') as $element) {
       if ($element->innertext === "B") {
            $select = $element;
            break;   
       }
}
?>