filemtime "warning stat failed for"

I already read it so many questions and answers about it but I can't still solve my problem...

I'm trying to create a function that deletes all the files with "xml" or "xsl" extension that has been created one day ago. But I'm getting this warning on each file I have:

Warning: filemtime() [function.filemtime]: stat failed for post_1003463425.xml in /home/u188867248/public_html/ampc/library.php on line 44

All the files of this directory have the same structure name "post_ + randomNum + .xml" (example: post_1003463425.xml or post_1456463425.xsl). So I think it's not an encoded problem (like I saw in other questions).

The code of my function is this:

 function deleteOldFiles(){
    if ($handle = opendir('./xml')) {
        while (false !== ($file = readdir($handle))) { 

            if(preg_match("/^.*\.(xml|xsl)$/i", $file)){

                $filelastmodified = filemtime($file);

                if ( (time()-$filelastmodified ) > 24*3600){
                    unlink($file);
                }
            }
        }
        closedir($handle); 
    }
}

Thanks for your help :)

I think the problem is the realpath of the file. For example your script is working on './', your file is inside the directory './xml'. So better check if the file exists or not, before you get filemtime or unlink it:

  function deleteOldFiles(){
    if ($handle = opendir('./xml')) {
        while (false !== ($file = readdir($handle))) { 

            if(preg_match("/^.*\.(xml|xsl)$/i", $file)){
              $fpath = 'xml/'.$file;
              if (file_exists($fpath)) {
                $filelastmodified = filemtime($fpath);

                if ( (time() - $filelastmodified ) > 24*3600){
                    unlink($fpath);
                }
              }
            }
        }
        closedir($handle); 
    }
  }