Php 5.6 “Automatically populating $HTTP_RAW_POST_DATA is deprecated”

The following warning is a known issue when running on PHP 5.6:

“Automatically populating $HTTP_RAW_POST_DATA is deprecated”

You can fix it by setting “always_populate_raw_post_data” to “-1” in the php.ini file.

Other alternative is to upgrade to PHP 7.0.

Reference: https://github.com/matomo-org/matomo/issues/6465