code: public function offsetUnset($offset)
      {
          $task = function() use ($offset) {
              $keyMapper = $this->getKeyMap();
              if(array_key_exists($offset,$keyMapper)) {
                  shm_remove_var($this->id, $keyMapper[$offset]);
                  unset($keyMapper[$offset]);
                  shm_put_var($this->id, 0, $keyMapper);
              }
          };
          
          $this->lockExecute($task);
      }
docs: (PHP 5 &gt;= 5.0.0)<br/>
  Offset to unset
  @link http://php.net/manual/en/arrayaccess.offsetunset.php
  
  @param mixed $offset <p>
  The offset to unset.
  </p>
  
  @return void