Remove Stuff From Footer

function mu_footer_filter(){
    function my_start_footer_ob() {
        ob_start("my_end_footer_ob_callback");
    }
    add_action('wp_footer', 'my_start_footer_ob');

    function my_end_footer_ob() {
        ob_end_flush();
    }
    add_action('wp_footer', 'my_end_footer_ob', 1000);

    function my_end_footer_ob_callback($buffer) {
        /** The Following Preg replace / Buffer Does Not Work **/
        //$buffer = preg_replace('/<div id=\"test\">.*<\/div>/', 'asdf', $buffer);
        //return $buffer;

        /** The HTML Portion does not work **/
        $doc = new DOMDocument;
        $doc->loadHTML($buffer);

        $docElem = $doc->getElementById("test");

        if($docElem !== NULL) // if it exists
            $docElem->parentNode->removeChild($docElem);

        return $doc->getElementsByTagName('body')->firstChild->nodeValue;
    }
}
add_action('muplugins_loaded', 'mu_footer_filter');

function test(){
    $test = '<div id="test">test</div>';
    // $test = preg_replace('/<div id=\"test\">.*<\/div>/', '', $test); // This Preg Replace is functional.
    echo $test;
}
add_action('wp_footer', 'test');