Here are the steps when you found yourself in this situation.

1. Kill the server process.
% kill pid
(where pid is the process id. Do not use kill -9 unless absolutely
necessary, as this may damage your table files)

2. Run safe-mysqld with the –skip-grant-tables command line option.
(This instructs the MySQL server to allow unrestricted access to
anyone) NOTE: restrict all remote access before issuing this command
% safe-mysqld --skip-grant-table

3. Change root password
mysql > use mysql;
mysql > update user set password = password('newpassword') where user
= 'root';

4. Disconnect and instruct the mysql server to reload the grants
tables to begin requiring passwords.
% mysqladmin flush-privileges

“That does it — and nobody ever has to know what you did. As for
locking your keys in your car, you’re on your own there.”

Must have for php-mysql beginners developers.