public function exists($key)
    {
        $this->init();
        $result = $this->driver->exists($key);
        return (bool)$result;
    }
public function exists($key)
    {
        $this->init();
        $result = $this->driver->exists($key);
        return (bool)$result;
    }
public function exists ( $ key ) { $ this -> init ( ) ; $ result = $ this -> driver -> exists ( $ key ) ; return ( bool ) $ result ; }
Determine if a key exists
@param string $key
@return boolean
Determine if a key exists