Weather map problem

[paheocon]

I have this problem after install weathermap 0.97c on ubuntu 16.04 and cacti 0.8.8f:

The map config directory is not writable by the web server user. You will not be able to edit any files until this is corrected. [WMEDIT01]<p>

I try some command like:

chmod -R 777 /usr/share/cacti/site/plugins/weathermap/configs

But in the end seem like the problem was fixed but when i click add not weather map turn out blank page forerver. Can u guy help me solve this problem

I check PHP in CLI: php check.php and this is shown up:
PHP Functions
-------------
Some parts of Weathermap need special support in your PHP
installation to work.

This PHP uses the system GD library, which MIGHT have alpha-blending bugs.
Check that you have at least GD 2.0.34 installed, if you see problems with
weathermap segfaulting.
You can test for this specific fault by running check-gdbug.php

The Console_Getopt PEAR module is available. That's good!

PHP Fatal error: Uncaught Error: Call to undefined function split() in /usr/share/cacti/site/plugins/weathermap/check.php:195
Stack trace:
#0 {main}
thrown in /usr/share/cacti/site/plugins/weathermap/check.php on line 195