Your PHP does not seem to install the MySQL extension necessary to run WordPress

Php-i | grep Extension_dir

[Email protected]:/usr/lib/php/20151012# apt-get Install Php-mysql
Reading Package Lists ... Done
Building Dependency Tree
Reading state information ... Done
The following additional packages'll be installed:
Php7.0-mysql
The following NEW packages'll be installed:
Php-mysql Php7.0-mysql
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 126 KB of archives.
After this operation, 488 KB of additional disk space would be used.
Want to continue? [y/n] Y
Get:1 http://mirrors.aliyun.com/ubuntu xenial-updates/main amd64 php7.0-mysql amd64 7.0.18-0ubuntu0.16.04.1 [124 KB]
Get:2 Http://mirrors.aliyun.com/ubuntu xenial/main amd64 php-mysql all 1:7.0+35ubuntu6 [1,936 B]
fetched 126 kB in 0s (438 kb/s)
Selecting previously unselected package php7.0-mysql.
(Reading database ... 111452 files and directories currently installed.)
Preparing to unpack .../php7.0-mysql_7.0.18-0ubuntu0.16.04.1_amd64.deb ...
Unpacking Php7.0-mysql (7.0.18-0ubuntu0.16.04.1) ...
Selecting previously unselected package php-mysql.
Preparing to unpack .../php-mysql_1%3a7.0+35ubuntu6_all.deb ...
Unpacking Php-mysql (1:7.0+35UBUNTU6) ...
Processing triggers for libapache2-mod-php7.0 (7.0.18-0ubuntu0.16.04.1) ...
Processing triggers for PHP7.0-FPM (7.0.18-0ubuntu0.16.04.1) ...
Setting up Php7.0-mysql (7.0.18-0ubuntu0.16.04.1) ...

Creating config File/etc/php/7.0/mods-available/mysqlnd.ini with new version

Creating config File/etc/php/7.0/mods-available/mysqli.ini with new version

Creating config File/etc/php/7.0/mods-available/pdo_mysql.ini with new version
Setting up Php-mysql (1:7.0+35UBUNTU6) ...
Processing triggers for libapache2-mod-php7.0 (7.0.18-0ubuntu0.16.04.1) ...
Processing triggers for PHP7.0-FPM (7.0.18-0ubuntu0.16.04.1) ...
[Email protected]:/usr/lib/php/20151012#/usr/local/apache/bin/apachectl Stop
-bash:/usr/local/apache/bin/apachectl:no such file or directory
[Email protected]:/usr/lib/php/20151012# apachectl
Usage:/usr/sbin/apachectl start|stop|restart|graceful|graceful-stop|configtest|status|fullstatus|help
/usr/sbin/apachectl <apache2 args>
/usr/sbin/apachectl-h (for help on <apache2 args>)
[Email protected]:/usr/lib/php/20151012# apachectl Stop
AH00558:apache2:Could not reliably determine the server ' s fully qualified domain name, using 10.173.21.106. Set the ' ServerName ' directive globally to suppress this message
[Email protected]:/usr/lib/php/20151012#/etc/init.d/apache2 Restart
[OK] Restarting Apache2 (via Systemctl): Apache2.service.

Your PHP does not seem to install the MySQL extension necessary to run WordPress