Note: implode() can, for historical reasons, accept
its parameters in either order. For consistency with
explode(), however, it may be less confusing
to use the documented order of arguments.
Note:
As of PHP 4.3.0, the glue parameter of implode() is
optional and defaults to the empty string(''). This is not the preferred
usage of implode(). We recommend to always use two
parameters for compatibility with older versions.
