I am facing this issue on one of my website deployed on production. I am having cpanel access to hosting but can only upgrade php version (currently its 5.6 default). I can't upgrade php version to php7 as of now, as it will require to update so many things in source code due to incompatibility.
Client API library version => 10.5.11 Client API header version => 10.3.11-MariaDB
I tried other solution suggested in similar questions before but still couldn't resolve this issue. I tried to disable mysql and enabled mysqlnd as suggested in this link but no change using cpanel. As per this answer given here, I am unable to get it how should I revert back mysql client libraries using cpanel?
I am not able to understand how should I upgrade Client API header version so that it matches with Client API library version.
Other info that I found by running php -i on cpanel terminal is as follows:
mysqli
MysqlI Support => enabled
Client API library version => 10.5.11
Active Persistent Links => 0
Inactive Persistent Links => 0
Active Links => 0
Client API header version => 10.3.11-MariaDB
MYSQLI_SOCKET => /var/lib/mysql/mysql.sock