PHP file_exists function intermittendly fails to detect if file exists

Question

Other posts have suggested using an absolute (full) path. I appear to do this.

Another post admitted using a virtual server. I am not doing that.

This is my code.

    $dt=date("Y.m.d");
    $tm=date("H:i:s");
    $ip=$_SERVER['REMOTE_ADDR'];
    $variables_directory='variables';
    $root_path=dirname($_SERVER['SCRIPT_FILENAME']);
    $pathdir0=$root_path.'/'.$variables_directory;
    $old_umask = umask(0);
    if(!file_exists($pathdir0))@mkdir($pathdir0, 0777,true);
    $pathdir1=$pathdir0.'/'.$dt;
    if(!file_exists($pathdir1))@mkdir($pathdir1, 0777,true);
    $pathdir2=$pathdir1.'/'.str_ireplace(':','',$tm);
    if(!file_exists($pathdir2))@mkdir($pathdir2, 0777,true);
    $pathdir3=$pathdir2.'/'.$ip;
    if(!file_exists($pathdir3))@mkdir($pathdir3, 0777,true);     // <<<<<

This code exists on a live site which uses error handling to catch errors and warnings. I often receive the following Unhandled Warning.

Line: 4956

Message: mkdir() [function.mkdir]: File exists

I have highlighted Line 4956 in the above section of code with <<<<<.

These warning messages which are emailed to me are really annoying.

Any ideas on how to stop the condition from occurring?