PHP warning in alpine dockers in Administration->Backup script

[bradymiller]

In both alpine dockers the Administration->Backup features are working as expected. However do see following php warnings (these are not seen in ubuntu dockers):

[30-Oct-2017 18:22:31 UTC] PHP Warning:  include_once(Archive/Tar.php): failed to open stream: No such file or directory in /var/www/localhost/htdocs/openemr/interface/main/backup.php on line 51
[30-Oct-2017 18:22:31 UTC] PHP Warning:  include_once(): Failed opening 'Archive/Tar.php' for inclusion (include_path='.:') in /var/www/localhost/htdocs/openemr/interface/main/backup.php on line 51

[bradymiller]

I think php7-pear will solve this. Will test this soon. Note that avoiding this warning is not necessary, but would be ideal(and if do get rid of warning, then need to retest all the backup scripts since the mechanism is a little different when the Tar.php is available).