RSS Feed Looks Different - IE vs FF

My RSS feed looks different depending on if you look at it in FireFox or Internet Explorer.

You can see the feed here: http://www.wizardrss.com/cache/rss.php

Internet Explorer is displaying it correctly but FireFox is not. The feeds should be listed in the order in which they were posted.

The way the feed works: it shows the files that are in the cached folder based upon when they were lasted modified.

Could anyone please take a look at the code and let me know what I am doing wrong:

<?php
 
	 
	 /* Basic Feed Info*/
	 $title = "Full Text RSS Feeds"; //Title for your RSS feed
	 $link  = "http://www.wizardrss.com/";  //Link to your main site for the feed
	 $description = "Full Text RSS Feeds";	//Brief description of your feed
	 $link_base   = "http://www.wizardrss.com/cache/";	//Base URL for linking files (INCLUDE ENDING SLASH!!!)
	 $feed_url    = "http://www.wizardrss.com/cache/rss.php";	//Full URL to the rss.php file
	 $language    = "en"; 	//Feed language (en = English)
	 $ttl		  = "5"; 	//TTL setting
	 
	 
	 /* Feed Image */
	 $image_url = "";	//URL to your feed image. Ex: http://www.yourdomain.com/images/rss.jpg
	 $image_title = $title;
	 $image_link = $link;	 
	 
	 
	 /* Script/Directory Info */
	 $rss_file_name = "rss.php";	//This needs to be changed if you are changing the name of this file
	 
	 $dir = "./";	//Directory to list contents from (must be path). Set to "." for current directory
	 				//Leave empty to auto-detect
					
	$default_sort = "date";		//Default sorting method for RSS feed
								// date: most recent to oldest
								// odate: oldest to most recent
								// Leave blank for server default
								//
								//These settings can be over-ridden by appending ?sort={sorting-option-here} to the URL when viewing the script (DISABLED IN DEMO)


	 /* Filtering Details */
	 $allow = array(		//enter file extensions - all others will be ingored (do NOT include the "." in the extension)
					"pdf",		//PDF Docs
					//"doc",	//Word Docs
					//"docx",	//Word 2007+ Docs
					//"xls",	//Excel Docs
					//"xlsx",	//Excel 2007+ Docs
					//"ppt",	//Power Point Docs
					//"pptx",	//Power Point 2007+ Docs
					//"jpg",	//JPG images
					//"gif",	//GIF images
					//"png",	//PNG images
					//"php",	//PHP Pages
					"xml",	//XML Pages

					);
	 $allow_all = false;	//Override the above settings - set to true to enable all files to be displayed
	 
	 
	 //DISABLED IN DEMO VERSION!!!
	 $filter = array(	//enter any files you don't want displayed here
					 $rss_file_name,	//This file
					 "..",		//Up Directory Link
					 ".",		//Current Directory Link
					 ".htaccess", 	//.htaccess file
					 ".passwd",		//.passwd file
					 //"config.php",	//example configuration file
					 //"error_log",	//example error log
					 //"some_private_file.pdf",	//Another example
					 
					 );
	 
	 
	 
	 /* YOU SHOULDN'T HAVE TO MODIFY ANYTHING BELOW THIS LINE */
	 
header('Content-type: text/xml');
echo "<?xml version=\"1.0\" encoding=\"ISO-8859-1\"?>"; ?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
	<channel>
		<title><?php echo stripslashes($title); ?></title>
		<link><?php echo stripslashes($link); ?></link>
		<description><?php echo stripslashes($description); ?></description>
		<language><?php echo stripslashes($language); ?></language>

		<lastBuildDate><?php echo date("r",time()); ?></lastBuildDate>
		<generator>EndsDesign.com</generator>
		<ttl><?php echo stripslashes($ttl); ?></ttl>
		<?php if(!empty($image_url)) { ?><image>
			<url><?php echo stripslashes($image_url); ?></url>
			<title><?php echo stripslashes($image_title); ?></title>

			<link><?php echo stripslashes($image_link); ?></link>
		</image><?php } ?>
        <atom:link href="<?php echo $feed_url; ?>" rel="self" type="application/rss+xml" />
        <?php
		
		//Auto-Detect Directory
		if(empty($dir)) {
			$dir = $_SERVER['SCRIPT_FILENAME'];
			$dir = str_replace($rss_file_name,'',$dir);
		}
		
		$contents = array();
		$file_link = array();
		$i = 0;
		// Open a known directory, and proceed to read its contents
		if (is_dir($dir)) {
			if ($dh = opendir($dir)) {
				while (($file = readdir($dh)) !== false) {
					if($i > 9) { break; } 
					$ext = substr($file, strrpos($file, '.') + 1);
					if(in_array($ext,$allow) || $allow_all) {	//exclusions
						$contents[$i] = filemtime($dir.$file);
						$file_link[$i] = $file;
						$i++;
					}
				}
				
				$sort = $default_sort;
				
				foreach($contents as $k=>$v) {
					$file = $file_link[$k];
					?>
						<item>
							<title><?php echo $file; ?></title>
							<link><?php echo $link_base.str_replace(' ','%20',$file); ?></link>
                            <guid><?php echo $link_base.str_replace(' ','%20',$file); ?></guid>
							<pubDate><?php echo date("r",filemtime($file)); ?></pubDate>
							<description>Full Text RSS Feeds - Powered by WizardRSS</description>
						</item>					
                    <?php
				}
				
					?>
                    <?php
				closedir($dh);
			}
		}	
		?>
	</channel>
</rss>

Code (markup):

Please and thank you

 

Nothing seems problem here!
Is listed in Date wise in my FireFox