<?php 
$sessionDir = "/tmp/";  // your sessions directory 
$compareTime = time() - 10800;  // 3 hours 
$count = 0; 
foreach (glob($sessionDir . "*.sess") as $file) 
  if ($compareTime >= filemtime($file)) 
    if (unlink($file)) $count++;  
echo "$count session files were deleted"; 
?>