I need to open my database through PHP. But I need to know my username and the name of my host (e.g. localhost), and I don't know them.
When I used mysql and did my database, it just asked me directly for a password.
How do I find my host and username on mysql?
The default username is root. You can reset the root password if you do not know it: http://dev.mysql.com/doc/refman/5.0/en/resetting-permissions.html. You should not, however, use the root account from PHP, set up a limited permission user to do that: http://dev.mysql.com/doc/refman/5.1/en/adding-users.html
If MySql is running on the same computer as your webserver, you can just use "localhost" as the host
You should be able to access the local database by using the name localhost. There is also a way to determine the hostname of the computer you're running on, but it doesn't sound like you need that. As for the username, you can either (1) give permissions to the account that PHP runs under to access the database without a password, or (2) store the username and password that you need to connect with (hard-coded or stored in a config file), and pass those as arguments to mysql_connect. See http://php.net/manual/en/function.mysql-connect.php.
