How do I send mails with PHP?

PHP has a function called mail for that purpose, example (from php.net):

mail("nobody@example.com", "the subject", $message,
"From: webmaster@$SERVER_NAME\r\n"
."Reply-To: webmaster@$SERVER_NAME\r\n"
."X-Mailer: PHP/" . phpversion());

For more information about the function look here:
http://www.php.net/manual/en/ref.mail.php

I have lost my MySQL root password, how can I get in?

If you have forgotten the root user password for MySQL, you can restore it with the following procedure:

Take down the mysqld server by sending a kill (not kill -9) to the mysqld server.

The pid is stored in a .pid file, which is normally in the MySQL database directory:
kill `cat /mysql-data-directory/hostname.pid`

You must be either the Unix root user or the same user the server runs as to do this.

Restart mysqld with the --skip-grant-tables option.

Connect to the mysqld server with mysql -h hostname mysql and change the password with a GRANT command.

See section 7.35 GRANT and REVOKE Syntax http://www.mysql.com/doc/G/R/GRANT.html

You can also do this with mysqladmin -h hostname -u user password 'new password'

Load the privilege tables with: mysqladmin -h hostname flush-privileges or with the SQL command FLUSH PRIVILEGES.

Note that after you started mysqld with --skip-grant-tables, any usage of GRANT commands will give you an Unknown command error until you have executed FLUSH PRIVILEGES.