Write to XML file using fopen in Wordpress - php

Question

I'm trying to write to an XML file in the uploads folder in my Wordpress directory. This XML needs to update each time the client updates or creates a new post using a custom post_type I created.
Here is the code:
<?
add_action( 'save_post', 'producers_xml' );
function producers_xml(){
if ($_POST['post_type'] == 'producer')
{
$xml = new SimpleXMLElement('<xml/>');
$producers = get_posts( array( 'post_type'=>'producer', 'numberposts'=>-1 ) );
$xml->addChild('producers');
foreach($producers as $i=>$producer){
$name = get_the_title($producer->ID);
$owner = get_post_meta($producer->ID, '_producer_contact_name', true);
$phone = get_post_meta($producer->ID, '_producer_phone', true);
$fax = get_post_meta($producer->ID, '_producer_fax', true);
$email = get_post_meta($producer->ID, '_producer_email', true);
$website = get_post_meta($producer->ID, '_producer_website', true);
$address = get_post_meta($producer->ID, '_producer_address', true);
$xml->producers->addChild('producer');
$xml->producers->producer[$i]->addChild('name', $name);
$xml->producers->producer[$i]->addChild('owner', $owner);
$xml->producers->producer[$i]->addChild('phone', $phone);
$xml->producers->producer[$i]->addChild('fax', $fax);
$xml->producers->producer[$i]->addChild('email', $email);
$xml->producers->producer[$i]->addChild('website', $website);
$xml->producers->producer[$i]->addChild('address', $address);
}
$file = '../../../uploads/producers.xml';
$open = fopen($file, 'w') or die ("File cannot be opened.");
fwrite($open, $xml->asXML());
fclose($open);
}
}
?>
The problem I am having is that it keeps giving me the "File cannot be opened." error that I supplied. My uploads folder (and all enclosed items) have full permissions (777). I've tested my code locally and it works, but I can't get it to open that file on the remote server. I don't have root access to it so I can't change permissions on anything before httpdocs.
I should also mention that fopen is enabled on the server.
EDIT: allow_url_fopen is enabled but allow_url_include is disabled.
Anybody know what my problem is?
Thanks

Answer 1

Try using an absolute path (full path), alongside other checks see:
$file = 'home/my/path/uploads/producers.xml'; //Absolute path
if(is_file($file) && is_readable($file)){
$open = fopen($file, 'w') or die ("File cannot be opened.");
fwrite($open, $xml->asXML());
fclose($open);
}