PHP flock() alternative

Question

PHP\'s documentation page for flock() indicates that it\'s not safe to use under IIS. If I can\'t rely on flock under all circumstances, is there another way I

Answer 1

Based on mkdir:

// call this always before reading or writing to your filepath in concurrent situations
function lockFile($filepath){
   clearstatcache();
   $lockname=$filepath.".lock";
   // if the lock already exists, get its age:
   $life=@filectime($lockname);
   // attempt to lock, this is the really important atomic action:
   while (!@mkdir($lockname)){
     if ($life)
        if ((time()-$life)>120){
           //release old locks
           rmdir($lockname);
     }else $life=@filectime($lockname);
     usleep(rand(50000,200000));//wait random time before trying again
   }
}

To avoid deadlock when one script in case a script exits before it has unlocked and one (or more scripts) at the same time have no result on $life=@filectime($lockname); because all scripts starts at the same time and then directory isn't created yet. To unlock then call:

function unlockFile($filepath){
   $unlockname= $filepath.".lock";   
  return @rmdir($unlockname);
}