php7.4 mysqli times out with "gone away"

Question

I have just installed php7.4, everything seems ok but when I try to go on my phpmyadmin, I can't : Note works fine in php7.3 before this installation

The error is :

mysqli_real_connect(): Unexpected server response while doing caching_sha2 auth: 109
 mysqli_real_connect(): (HY000/2006): MySQL server has gone away

looking my php mysql library :php7.4-mysql. it's installed.

Forget something ? Thank you.

NOTICE: Not enabling PHP 7.4 FPM by default.
NOTICE: To enable PHP 7.4 FPM in Apache2 do:
NOTICE: a2enmod proxy_fcgi setenvif
NOTICE: a2enconf php7.4-fpm
NOTICE: You are seeing this message because you have apache2 package installed.
Traitement des actions différées (« triggers ») pour libapache2-mod-php7.4 (7.4.
0-1+ubuntu19.10.1+deb.sury.org+1) ...

apt-cache policy php7.4
php7.4:
  Installé : 7.4.0-1+ubuntu19.10.1+deb.sury.org+1
  Candidat : 7.4.0-1+ubuntu19.10.1+deb.sury.org+1
 Table de version :
 *** 7.4.0-1+ubuntu19.10.1+deb.sury.org+1 500
        500 http://ppa.launchpad.net/ondrej/php/ubuntu eoan/main amd64 Packages
        500 http://ppa.launchpad.net/ondrej/php/ubuntu eoan/main i386 Packages
        100 /var/lib/dpkg/status

Answer 1

I had the same issue, but using mysql_native_password was not possible with PHP7.4-mysql-pdo, even on setting in my.cnf as it worked on PHP7.3-mysql-pdo.

I had to alter every user with this query:

ALTER USER 'username'@'localhost' IDENTIFIED WITH caching_sha2_password BY 'password';

where username is the database username and password is the password of the database user.