If 1st XML is empty then load a different one - php

Question

Im getting the contents of an xml feed and printing the titles on my web page with php:
$url = 'http://site.com/feed';
$xml = simplexml_load_file($url);
foreach($xml->ART as $ART) {
echo $ART->TITLE;
}
I want to be able to set a backup, so if the first xml isn't found a different one is loaded instead.
I tried the following code but it doesn't work. If the feed isnt found the page shows 'XML Parsing Error:' which i guess isnt the same as nothing.
if ($url != '') {
$xml = simplexml_load_file($url);
} else {
//Here I would load a different xml file.
}
What should I do? Should I write conditional php to check if the first url contains a TITLE, and if not load the 2nd url?
Thanks
UPDATE
This messed up my whole page:
$first_url = 'http://site.com/feed1';
$second_url = 'http://site.com/feed2';
// if URL wrappers is enabled
if (is_url($first_url))
{
// parse first url
$xml = simplexml_load_file($first_url);
}
else
{
// parse second url
$xml = simplexml_load_file($second_url);
}
foreach($xml->ART as $ART) {
echo $ART->TITLE;
}

Answer 1

See simplexml_load_file
Returns an object of class SimpleXMLElement with properties containing the data held within the XML document. On errors, it will return FALSE.
Example from php.net
<?php
// The file test.xml contains an XML document with a root element
// and at least an element /[root]/title.
if (file_exists('test.xml')) {
$xml = simplexml_load_file('test.xml');
print_r($xml);
} else {
exit('Failed to open test.xml.');
}
?>
EDIT: you can do
$url = 'http://site.com/feed';
if( $xml = simplexml_load_file($url) ) {
foreach($xml->ART as $ART) {
echo $ART->TITLE;
}
} else {
//parsing new url
}

Answer 2

function parse_xml($url)
{
// your code
}
try
{
parse_xml($first_url);
}
catch (Exception $e)
{
parse_xml($second_url);
}
Alternatively, you can do a check if the URL return XML before proceed to parsing :-
// if URL wrappers is enabled
if (is_url($first_url))
{
// parse first url
$xml = simplexml_load_file($first_url);
}
else
{
// parse second url
$xml = simplexml_load_file($second_url);
}

Answer 3

Think ive got it working with:
$url = 'site.com/feed1';
$xml = simplexml_load_file($url);
if ($xml == null) {
$url = 'site.com/feed2';
$xml = simplexml_load_file($url);
}
foreach($xml->ART as $ART) {
echo $ART->TITLE;
}