Extract text between page breaks in TEI with PHP

extract.php

   $nodes = $xp->query('/tei:TEI/tei:text//node()[self::text() or self::tei:pb]');
    for($n = 0; $n < $nodes->length; $n++) {
        $node = $nodes->item($n);
        if($node instanceof DOMNode && $node->nodeType === XML_ELEMENT_NODE) {
            $pageCount++;
            $content = preg_replace("/[[:space:]]{2,}/u", ' ', $text) . "\n";
            $fn = sprintf("%s/%s_%04d", $dir, $id, $pageCount);
            file_put_contents($fn, $content);
            $text = '';
        }
        if($node instanceof DOMText) {
            $text .= $node->textContent . " ";
        }
    }