file_put_contents & simplexml

[scrupul0us]

im trying to cache xml to a file... see code below:

function getDomains($url)
{

$cache_time = 300; //time in seconds

if(!file_exists('domains.xml'))
{
	$xml = simplexml_load_string($url); //parser error : Start tag expected, '<' not found in
	file_put_contents('domains.xml',$xml);
	$xml = simplexml_load_file('domains.xml');
	return $xml;
}
elseif(file_exists('domains.xml'))
{
	$modified = @filemtime('domains.xml');
	$now = strtotime("now");
	$difference = $now - $modified;

	if ($difference >= $cache_time)
	{
		$xml = simplexml_load_string($url);
		file_put_contents('domains.xml',$xml);
		$xml = simplexml_load_file('domains.xml');
		return $xml;
	}
	else
	{
		$xml = simplexml_load_file('domains.xml');
		return $xml;
	}		
}
}

am i fudging this up somehow?

[NogDog]

Instead of the file_put_contents():

$xml->asXML('domains.xml');

PS: There's really no reason to then read the file again since you just wrote it, is there? You could just return $xml after that.