PHP并不总能找到XML文件

Question

I looked around for similar questions but found none identical, so here goes:

I have this webpage on a linux/apache server, the PHP script opens a XML-file upon every execution, the funny thing is that sometimes it can read the file and on some rare occasions it can not.. And when it cannot read it says that the file does not exist and to fix it I just have to refresh the page.

The XML file can be found in a sub directory (e.g. /srv/www/page/subdir/file.xml) and can only be changed manually and have the right privileges set (PHP can read and write to it).

I am using simplexml and the error I get is: I/O warning : failed to load external entity

So something strange is going on in the server, I just can't figure out what..

Edit: Adding some code

if ( !file_exists( $file ) )
{           
    error_log("File " . $file . " does not exist!");
    //return FALSE;
}

if ( $obj = simplexml_load_file( $file ) )
{
    // do stuff
    return TRUE;
}
else
{
    error_log("Could not parse XML: " . $file );
    return FALSE;
}

---

Solved: error in code, not server

Answer 1

There are no obvious explanation why the file is occasionally unavailable. Could be a platform/OS issue, it's hard to tell.

However, you could apply this band-aid on the problem, it may unblock you if waiting up to 3 seconds makes the file "re-appear":

$count = 0;
$found = FALSE;
while( $count < 3 && !$found ) {
   if ( !file_exists( $file ) ) {
      $count++;
      sleep( 1 ); // sleep 1 second to see if the file appears on the next try
   } else
      $found=TRUE;
}

if( !$found )
  die("file not found after 3 attempts");