Can’t log into phpMyAdmin: mysqli_real_connect(): (HY000/1698): Access denied for user ‘root’@’localhost’

1 Create a New Superuser for phpMyAdmin
In terminal, log in to MySQL as root. You may have created a root password when you installed MySQL for the first time or the password could be blank.

sudo mysql -p -u root

Now add a new MySQL user with the username of your choice. In this example we are calling it pmauser. Make sure to replace password_here with your own.
The command below will create a new user called pmauser (call this what you like) which can access the MySQL server from localhost with the password password_here.

CREATE USER 'pmauser'@'localhost' IDENTIFIED WITH mysql_native_password BY 'password_here';

Now we will grant superuser privilege to our new user pmauser.

GRANT ALL PRIVILEGES ON *.* TO 'pmauser'@'localhost' WITH GRANT OPTION;