Is it not possible to use PHP and grab an XML file? - php

Question

Why can't I use PHP in an .xml file at the same time grab it with SimpleXMLElement? When one works, the other doesn't.
Example: If I use PHP in the .xml file like
file.xml.php
<?php
require('db.php');
header('Content-Type: application/xml; charset=utf-8');
$updated_date = date('l', filemtime('file.xml.php'));
?>
<?xml version="1.0" encoding="UTF-8" ?>
<content>
<value name="Content 1" val="Value 1"></value>
<value name="Content 2" val="Value 2"></value>
<value name="Content 3" val="Value 3"></value>
<value name="Last Updated" val="<?php echo $updated_date; ?>"></value>
</content>
It works fine. But if I use SimpleXMLElement to get the file:
$xmlstring = file_get_contents('file.xml');
$xmlObject = new SimpleXMLElement($xmlstring);
foreach($xmlObject->children() as $node) {
$arr = $node->attributes();
echo $arr['name'] . ':' . $arr['val'];
}
it gives me this error:
PHP Fatal error: Uncaught exception 'Exception' with message 'String could not be parsed as XML' in /var/www/html/get_xml.php:336\nStack trace:\n#0 /var/www/html/get_xml.php(336): SimpleXMLElement->__construct('<?php??require(...')\n#1 {main}\n
I know it's telling me that the xml file cannot be read. However, when I read the xml file through its own URL, it works fine as if it was just another xml file.
Is it not possible to use PHP in .xml files and grab them at the same time? Without PHP, the file is kind of useless to me. Unless if I can just use the plain name so that it doesn't show that error. I know it has to do something with the require.

Answer 1

When you're getting the file, you need to ensure it's actually being parsed by PHP first. If you're just getting the PHP/XML source file from disk, it will still contain the PHP code: The code won't have been executed, meaning you'll simply have an invalid XML file.
As you've already found out, grabbing the file in a browser, it's fine: You can simulate this via PHP by using file_get_contents($urlToTheXmlPhpFile). Note, this has to be a URL to the file via a webserver: If you're just using a path to a file on your local disk, this won't work and you'll have the same problem - PHP won't have executed the file, so it will be a malformed combination of XML and PHP still.
To clarify:
file_get_contents('myfile.xml.php'); // Malformed - Attempting to parse source code.
file_get_contents('http://mydomain/myfile.xml.php'); // This should work.
If you're simply trying to require the PHP XML file via your local filesystem, rather than via a webserver, you could use eval to execute the PHP code. Do so with caution though, as this has the potential to enable arbitrary code execution for anyone who is able to change the XML file.
$validXmlString = eval(file_get_contents('myfile.xml.php')); // Be careful with this.