Ubuntu – ” Access denied for user ‘phptheadmin’@’localhost’ ” while installing phptheadmin

Seems like your permissions aren't set right for root user or you have lost your MySQL root password.

I would try resetting MySQL password for root and trying again. I guess this is the fastest way. Follow these steps

step 1

Stop the mysql demon with this command

sudo /etc/init.d/mysql stop

step 2

Start the mysql demon process with following

sudo /usr/sbin/mysqld --skip-grant-tables --skip-networking &

(at this point it's safest to disable networking)

step 3

Start the mysql client with

mysql -u root

step 4

Then run following in mysql prompt, so you are able to change any password

FLUSH PRIVILEGES;

step 5

Then reset password with

 SET PASSWORD FOR root@'localhost' = PASSWORD('password');

step 6

In case you happen to have a mysql root account that can connect from everywhere, this is recommended

UPDATE mysql.user SET Password=PASSWORD('newpwd') WHERE User='root';

step 7

Once you receive a message indicating a succesful query, then run

FLUSH PRIVILEGES;

step 8

Stop mysql and relaunch it with

sudo /etc/init.d/mysql stop
sudo /etc/init.d/mysql start

I suppose you have these installed

web server apache

php

php_mysql support for apache

source: https://help.ubuntu.com/community/MysqlPasswordReset