I am using Debian Jessie here, and I have got a couple of PHP pages showing the error:A PHP Error was encounteredSeverity: WarningMessage: mysqli::real_connect(): Headers and client library minor version mismatch. Headers:50553 Library:50630Filename: mysqli/mysqli_driver.phpThe php5 package is 5.6.30+dfsg-0+deb8u1.The php5-mysql package is 5.6.30+dfsg-0+deb8u1.Both are standard Debian packages, and I have not compiled by hand any part of the components.I tried apt update and upgrade, reinstalling php5-mysql, and restarting Apache, but it did not solve the problem.phpinfo() also complains about mismatched versions in php5-mysql.What to do?
PHP throwing out an error version mismatch with MySQL plugin
debian;php
This seems a bug packaging php5-mysql; I found a related question in this post Headers and client library minor version mismatch.While not the accepted answer, the most pertinent answer in that link is:For new MySQL 5.6 family you need to install php5-mysqlnd, not  php5-mysql.Remove this version of the mysql driversudo apt-get remove php5-mysql And install this insteadsudo apt-get install php5-mysqlndHowever, for maintaining the consistency of dependencies, uninstalling php5-mysql is not the best of the ideas; it is much better doing:sudo apt-get install php5-mysqlndAnd letting the dependencies uninstall php5-mysql while installing php5-mysqlnd.From packages.debian.org: Package: php5-mysqlndMySQL module for php5 (Native Driver)This package provides modules for MySQL database connections directly  from PHP scripts. It includes the generic mysql module which can be  used to connect to all versions of MySQL, an improved mysqli module  for MySQL version 4.1 or later, and the pdo_mysql module for use with  the PHP Data Object extension.After doing sudo apt-get install php5-mysqlnd, the pages in question started working normally, without giving that warning.However, other legacy pages in another of the pages still using latin1 / iso-8859-1 started displayed funny letters e.g. being forced to UTF-8, so we had to rollback on that server to php5-mysql.