Comment # 2 on bug 1205162 from Petr Gajdos

Yes: mysqlnd is now built shared and has to be loaded.

However, I am trying to understand how your problem is caused. On a 15.4 system
I have at hand, phpinfo() gives:

<h2><a name="module_mysqli">mysqli</a></h2>
<table>
<tr class="h"><th>MysqlI Support</th><th>enabled</th></tr>
<tr><td class="e">Client API library version </td><td class="v">mysqlnd 7.4.33
</td></tr>
[...]
</table>
<h2><a name="module_mysqlnd">mysqlnd</a></h2>
<table>
<tr class="h"><th>mysqlnd</th><th>enabled</th></tr>
<tr><td class="e">Version </td><td class="v">mysqlnd 7.4.33 </td></tr>
[...]
</table>

and it is in sync with php -m.

This is thanks to /etc/php7/conf.d/_mysqlnd.ini which is supposed to load
mysqlnd.so extension _before mysqli.so (/etc/php7/conf.d/mysqli.ini).
/etc/php7/conf.d/* installed by php extension packages should be loaded
automatically by whatever sapi.