large String gets truncated when writing to dom node php

Question

I use the following code to write values to an xml file in php.

if(isset($_POST['title']) && isset($_POST['content'])){
    $news = new DOMDocument();
    $news->load('../files/news.xml');

    $parentNode = $news->getElementById('newsContainer');
    $newsNodes  = $news->getElementsByTagName('News');

    echo $_POST['content'];

    if($newsNodes->length > 0){
        $newsItem = $news->createElement('News');

        $newsItemTitle = $news->createElement('Title');
        $newsItemTitle->nodeValue = $_POST['title'];

        $newsItemContent = $news->createElement('Content');
        $newsItemContent->nodeValue = $_POST['content']; //The value I assign here gets cut out

        $newsItem->appendChild($newsItemTitle);
        $newsItem->appendChild($newsItemContent);
        $news->documentElement->appendChild($newsItem);

        $result = $news->save('../files/news.xml');

        if($result == FALSE){
            echo 'false';
        }else{
            echo 'true';
        }
    }else{
        $newNewsContentNode = new DOMDocument();

        $newsContainer = $newNewsContentNode->createElement('NewsContainer');
        $newsItem = $newNewsContentNode->createElement('News');

        $newsItemTitle = $newNewsContentNode->createElement('Title');
        $newsItemTitle->nodeValue = $_POST['title'];

        $newsItemContent = $newNewsContentNode->createElement('Content');
        $newsItemContent->nodeValue = $_POST['content']; //The value I assign here gets cut out

        $newsItem->appendChild($newsItemTitle);
        $newsItem->appendChild($newsItemContent);
        $newsContainer->appendChild($newsItem);

        $newNewsContentNode->appendChild($newsContainer);

        $result = $newNewsContentNode->save('../files/news.xml');

        if($result == FALSE){
            echo 'false';
        }else{
            echo 'true';
        }

    }

}

I save a string with 1065 characters in it but when I check the xml file the node contains only a part of the given string. I looked at the string which comes through the POST and it comes fine. What am I doing wrong here?

Please reduce your example code to demonstrate the issue to the point. That should also prevent you from posting unrelated code. And it should help to clear things up quick. / and just a note fyi: createElement in PHP allows you to pass the element value directly: https://secure.php.net/manual/en/domdocument.createelement.php — hakre, Jul 11 '15 at 20:34
If you see strings in node-values cut or dropped, this can be a character encoding issue. That normally become only visible at output. You have to provide valid UTF-8 strings, just assigning `$_POST` fields shows, that you're not checking for that. Related: [Regex to detect Invalid UTF-8 String](http://stackoverflow.com/q/11709410/367456) — hakre, Jul 11 '15 at 20:37

score 1 · Accepted Answer · answered Jul 12 '15 at 15:51

Do not use the DOMNode::$nodeValue or the second argument to DOMDocument::createElement() with variable values. Here is an escaping bug that can break the resulting XML.

$dom = new DOMDocument();
$dom->appendChild($dom->createElement("foo"));
$dom->documentElement->nodeValue = 'a & b';
echo $dom->saveXml();

Output:

Warning: main(): unterminated entity reference b in /tmp/execpad-145b170ab9f7/source-145b170ab9f7 on line 5
<?xml version="1.0"?>
<foo>a </foo>

You need to use DOMDocument::createTextNode() to avoid the problem.

$dom = new DOMDocument();
$dom->appendChild($dom->createElement("foo"));
$dom->documentElement->appendChild(
  $dom->createTextNode('a & b')
);
echo $dom->saveXml();

Output:

<?xml version="1.0"?>
<foo>a &amp; b</foo>

large String gets truncated when writing to dom node php

1 Answers1