Problem with occ upgrade

Hi,

I want migrating owncloud to nextcloud on OVH.
phpinfo.php on ovh say that it uses php 5.6.32.
I use php 5.6 but when I use this command : php5.6 ./occ upgrade

I get this error: “An unhandled exception has been thrown:
Doctrine\DBAL\DBALException: Failed to connect to the database: An exception occured in driver: could not find driver in /home/lisa/ici/www/owncloud/lib/private/DB/Connection.php:59”

php -v :
PHP 5.6.32-1+ubuntu16.04.1+deb.sury.org+2 (cli)

php -m :
[PHP Modules]
calendar
Core
ctype
curl
date
ereg
exif
fileinfo
filter
ftp
geoip
gettext
hash
iconv
igbinary
json
libxml
mbstring
memcached
mhash
msgpack
mysql
mysqli
mysqlnd
openssl
pcntl
pcre
PDO
pdo_mysql
Phar
posix
readline
redis
Reflection
session
shmop
sockets
SPL
standard
sysvmsg
sysvsem
sysvshm
tokenizer
xdebug
Zend OPcache
zlib
[Zend Modules]
Xdebug
Zend OPcache

How can I solve my error?

Thanks a lot for your help,

Kind regards