want to learn more about MySQL permissions, the table governing grants of those permissions to users, and how MySQL users are managed, refer to the “MySQL Reference Manual” (http://dev.mysql.com/doc/) and the sections on securing the initial MySQL accounts.
No set naming conventions exist for WordPress users or databases; hosting providers will typically append the name of the package or your account information to distinguish users that benefit from MySQL database co-tenancy. Again, it is possible to have multiple databases, owned by the same user or different MySQL users, running in a single MySQL database server instance. In the example shown in Figure 1.3, wp_ is used as a prefix for both usernames and database names, at least providing a hint to the database administrator that these belong to a WordPress installation. Security best practices recommend not using wp_ as your table prefix; this is covered more in Chapter 13.
What can go wrong between WordPress and MySQL? The following are the three primary root causes of installation failure. Note that all of these conditions need to be fulfilled at installation time; there has to be some basic database structure to contain the admin user before you can log in as that admin.
● Web server cannot find MySQL. Either you have the hostname for the MySQL server noted incorrectly in the wp-config.php file, or the web server is looking for a local MySQL instance and cannot open the socket connection to it. Here is a simple example: when you run WordPress locally on Mac OS, MySQL creates the socket /tmp/mysql.sock for local connections, but the WordPress PHP code is going to look for /var/mysql/mysql.sock through the PHP engine’s MySQL module. Simply symbolically link one to the other:
The actual filesystem path to the local MySQL socket is a function of the database configuration; when it starts up, it creates the local socket. Where the PHP engine, and therefore any PHP-based applications, looks for this socket is PHP configuration dependent. If you want to figure out exactly where the mismatch is, a bit of heavy-handed printf() style debugging helps.
Edit wp-includes/wp-db.php, the set of functions that establish WordPress’s database connection. If you are seeing the “Error establishing a database connection” message during installation, insert an echo(mysql_error()); statement where the error is detected to see the details displayed along with the generic message, as shown in Figure 1.6:
The mysql_error() function is a PHP library function that spits out the error generated by the last MySQL function called.
● WordPress finds MySQL but cannot log in. Most of the time, the MySQL username or password is wrong, particularly when you have to copy some arbitrary username generated by a hosting provider. Double-check your username data, and verify that it is reflected properly in your wp-config.php file. You may also run into a password authentication issue when using MySQL 4.1 or MySQL 5.0 with some web servers’ PHP implementations; they only support the older MySQL 4.0 password hashing scheme. If this is the case, use MySQL’s OLD_PASSWORD() function to hash your WordPress user’s password in the backward-compatible format; use the magic SQL incantation (at the MySQL command-line prompt or within the SQL window of MAMP) to address the following:
In this instance, user@host is your WordPress database username and database hostname, and password is the (clear text) password you provided in the configuration file.
● WordPress connects to MySQL but cannot select the database. Just because the web server can log in to the database server with your WordPress database user information does not mean that there is necessarily a database available to that user. This is another scenario best diagnosed with mysql_error(), by inserting it in wp-db.php where the selection error is identified:
If, after inserting the mysql_error() statement as described earlier, your attempts to complete installation result in an error box like that shown in Figure 1.7, your MySQL database was not created under the appropriate database user, or the database user does not have privileges to use it. Double-check what MySQL believes using the following command line:
Once you logged in as your designated MySQL database user, you did not see the MySQL database – in this case, it was probably created by the MySQL user root, and permissions to access or modify it were not granted to the WordPress installation’s MySQL user. If you have MySQL root access, or sufficient MySQL user privileges to create new databases within the MySQL instance, it is easy enough to create a database once logged in on the command line:
Again, it is important to distinguish operating system users from MySQL users from WordPress users. MySQL users are defined in the database and granted privileges to create databases, muck with tables, and otherwise generate useful data. WordPress users exist within the WordPress database tables created during install; they only have privileges, context, and meaning once you are logged in to WordPress.
Figure 1.6 mysql_error() reporting a socket problem
Figure 1.7 MySQL database selection error
Once you have a clean WordPress installation, you should see a collection of tables named according to the table prefix you set in wp-config.php; again, this is easy enough to verify using the MySQL command line:
In this example, you set the database table prefix to wp_; if you later add another WordPress installation using the same database user and instance, you can simply set a different prefix and have the two sites co-mingled in the same database table. You dig into the schema and uses of the basic WordPress database tables in Chapter 6. For now, once you are happily connected to MySQL, you are ready for some final clean-up and first-time administration.
FINISHING UP
At this point, your MySQL database is up and running. There is a home for your content, and your web server is happily executing the WordPress core code. There are just a couple more things to discuss.
Once you have completed the installation, proceed to log in with the credentials you set up in Figure 1.4 and you’ll see the basic WordPress Dashboard captured in Figure 1.8.
Figure 1.8 Dashboard view upon a first-time login
If you are not redirected to the Dashboard through the Log In button, or if you happen to visit your website’s top-level URL first, either click the Log In link on your website or explicitly go to the wp-admin subdirectory (example.com/wp-admin) to be presented with a login dialog box. Logging in to your website takes you to the WordPress Dashboard, which is both amazingly simple in its power and rich in its complexity and exposed features.
What you do next with the Dashboard depends on how happy you are with the basic installation. If, as in the preceding example, you ended up with an older version of WordPress, click the Update button to do an in-place upgrade to the latest distribution. In addition to having a strong self-installation feature, WordPress
