XML fails to load, without any errors message - php

Question

I have a XML structure in my PHP file.
For example:
$file = file_get_contents($myFile);
$response = '<?xml version="1.0"?>';
$response .= '<responses>';
$response .= '<file>';
$response .= '<name>';
$response .= '</name>';
$response .= '<data>';
$response .= base64_encode($file);
$response .= '</data>';
$response .= '</file>';
$response .= '</responses>';
echo $response;
If i create .doc file or with other extension and put little text in, it works. But, if user load file with complex structure (not only text) - XML just not load, and i have a empty file without errors.
But the same files works on my other server.
I have try use simplexml_load_string for output errors, but i have no errors.
The server with PHP 5.3.3 have the problem; the one with PHP 5.6 hasn’t. It works if I try it with 5.3.3 on my local server.
Is the problem due to the PHP version? If so, how exactly?

Answer 1

There're basically three things that can be improved in your code:
Configure error reporting to actually see error messages.
Generate XML with a proper library, to ensure you cannot send malformed data.
Be conservative in memory usage (you're currently storing the complete file in RAM three times, two of them in a plain text representation that depending of file type can be significantly larger).
Your overall code could like like this:
// Quick code, needs more error checking and refining
$fp = fopen($myFile, 'rb');
if ($fp) {
$writer = new XMLWriter();
$writer->openURI('php://output');
$writer->startDocument('1.0');
$writer->startElement('responses');
$writer->startElement('file');
$writer->startElement('name');
$writer->endElement();
$writer->startElement('data');
while (!feof($fp)) {
// If I recall correctly, substring size must be multiple of 4
// to encode it properly (except for last part)
$writer->text(base64_encode(fread($fp, 10240)));
}
$writer->endElement();
$writer->endElement();
$writer->endElement();
fclose($fp);
}
I've tried this code with a 316 MB file and used 256 KB on my PC.
As a side note, inserting binary files inside XML is pretty troublesome when files are large. It makes extraction problematic because you can't use most of the usual tools due to extensive memory usage.