code: protected function acquireLock($name, $timeout = 0)
      {
          $filePath = $this->getLockFilePath($name);
          return $this->retryAcquire($timeout, function () use ($filePath, $name) {
              $file = fopen($filePath, 'w+');
              if ($file === false) {
                  return false;
              }
  
              if ($this->fileMode !== null) {
                  @chmod($filePath, $this->fileMode);
              }
  
              if (!flock($file, LOCK_EX | LOCK_NB)) {
                  fclose($file);
                  return false;
              }
  
              // Under unix we delete the lock file before releasing the related handle. Thus it's possible that we've acquired a lock on
              // a non-existing file here (race condition). We must compare the inode of the lock file handle with the inode of the actual lock file.
              // If they do not match we simply continue the loop since we can assume the inodes will be equal on the next try.
              // Example of race condition without inode-comparison:
              // Script A: locks file
              // Script B: opens file
              // Script A: unlinks and unlocks file
              // Script B: locks handle of *unlinked* file
              // Script C: opens and locks *new* file
              // In this case we would have acquired two locks for the same file path.
              if (DIRECTORY_SEPARATOR !== '\\' && fstat($file)['ino'] !== @fileinode($filePath)) {
                  clearstatcache(true, $filePath);
                  flock($file, LOCK_UN);
                  fclose($file);
                  return false;
              }
  
              $this->_files[$name] = $file;
              return true;
          });
      }
docs: Acquires lock by given name.
  @param string $name of the lock to be acquired.
  @param int $timeout time (in seconds) to wait for lock to become released.
  @return bool acquiring result.