Seems like the upgrade to php5.6 via ppa messed up my php installation as now some packages have to be php-xxx, some are php5-xxx and some are php5.6-xxx. Another issue on the dashboard which appeared today guided me into the right direction:
Cronmanager encountered 1 Errors
The following commands failed with the listed error
/var/lib/asterisk/bin/module_admin listonline > /dev/null 2>&1 (1)
So i executed:
root@asterisk:~$ sudo -u asterisk /var/lib/asterisk/bin/module_admin listonlin
[FATAL] PEAR must be installed (requires Console/Getopt.php). Include path: .:/usr/share/php
root@asterisk:~$ sudo pear install db-1.7.14
sudo: pear: command not found
root@asterisk:~$ apt install php-pear
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/285 kB of archives.
After this operation, 2,186 kB of additional disk space will be used.
Selecting previously unselected package php-pear.
(Reading database ... 92702 files and directories currently installed.)
Preparing to unpack .../php-pear_1%3a1.10.5+submodules+notgz-1+ubuntu14.04.1+deb.sury.org+1_all.deb ...
Unpacking php-pear (1:1.10.5+submodules+notgz-1+ubuntu14.04.1+deb.sury.org+1) ...
Processing triggers for man-db (184.108.40.206-1ubuntu1) ...
Setting up php-pear (1:1.10.5+submodules+notgz-1+ubuntu14.04.1+deb.sury.org+1) ...
root@asterisk:~$ sudo pear channel-update pear.php.net
Updating channel "pear.php.net"
Update of Channel "pear.php.net" succeeded
root@asterisk:~$ pear install db-1.7.14
WARNING: "pear/DB" is deprecated in favor of "pear/MDB2"
downloading DB-1.7.14.tgz ...
Starting to download DB-1.7.14.tgz (134,864 bytes)
.............................done: 134,864 bytes
install ok: channel://pear.php.net/DB-1.7.14
and finally the "Apply config" from gui succeded. Is it possible to check for the existence of pear, php-prear or the pear/DB and have a more explicit error message in that case?
I added [Solved] to the title.