https://secure.php.net/manual/en/function.implode.php defines the order
of arguments as
string implode ( string $glue , array $pieces )
string implode ( array $pieces )
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.
Change-Id: I74468fe2833c897ec9a7ddeb5a1e5b50bb50da94
