Notice: Use of undefined constant WPLANG

Hi,
The PHP constant WPLANG should be used in the wp-config.php file, on the root of the WordPress directory. Have a look on the wp-config-sample.php file, you will notice there is such a constant.
Add this line on your wp-config.php file :
define('WPLANG', '');
or
define('WPLANG', 'en_GB');

Thanks for your message.
Sincerely,
Tony

Thanks for the answer.
Turns out WPLANG is now deprecated (since 4.0). You may still have it if you had your first install prior to 4.0, but WPLANG is no longer there since 4.0 (neither in wp-config-sample.php nor in wp-config.php).

Here is some info on this change – https://core.trac.www.ads-software.com/changeset/29630. It is recommended to use get_option('WPLANG') instead.

Here is a thread about it on Support forum – https://www.ads-software.com/support/topic/broken-wplang-_e-functions-not-selecting-good-language.

Cheers,
Dan

Thanks a lot for your information. I never noticed this change.
Thanks a again for your feedback.
I will fix this in a next release.

Have a nice day.
Sincerely,
Tony

Great, thank you so much for quick answers. Good luck with your plugins!