apache_note

test_apache_note.php

    if(!function_exists('apache_note')){
        echo 'apache_note'."don't exists";
    }
    if(!function_exists ( 'apache_setenv' )){
        echo 'apache_setenv'."don't exists";
    }
    apache_note('username', 'pedro_ok1' );
    apache_setenv('username', 'pedro_ok2',true);

000-default.conf

    ServerName localhost
    ServerAdmin webmaster@localhost
    DocumentRoot /var/www/html
    LogLevel debug
    #LogFormat "%{username}e" envuid_combined
    LogFormat "%{username}n" envuid_combined
    CustomLog ${APACHE_LOG_DIR}/access.log envuid_combined

and we get the log....

==> error.log <==
[Mon Dec 02 17:44:32.775175 2019] [authz_core:debug] [pid 6779] mod_authz_core.c(817): [client ::1:52962] AH01626: authorization result of Require all granted: granted
[Mon Dec 02 17:44:32.775196 2019] [authz_core:debug] [pid 6779] mod_authz_core.c(817): [client ::1:52962] AH01626: authorization result of : granted

==> access.log <==
pedro_ok1