MongoDB\BSON\Undefined::__toString
  (mongodb >=1.4.0)
MongoDB\BSON\Undefined::__toString — Returns an empty string
  
 
  Description
  
   final public MongoDB\BSON\Undefined::__toString
    ( void
   ) : string
  
 
  Parameters
  This function has no parameters.
  
 
  Return Values
  
   Returns an empty string.