Programming PHP

foreach ($movies as $movie) {
$id = $db->nextID('movies');
splice($movie, 0, 0, $id);
$db->query('INSERT INTO movies (id,title,year) VALUES (?,?,?)', $movie);
}
A sequence is really a table in the database that keeps track of the last-assigned ID.
You can explicitly create and destroy sequences with the createSequence( ) and
dropSequence( ) methods:
$res = $db->createSequence(sequence);
$res = $db->dropSequence(sequence);
The result will be the result object from the create or drop query, or DB_ERROR if an
error occurred.
Metadata
The getListOf( ) method lets you query the database for information on available
databases, users, views, and functions:
$data = $db->getListOf(what);
The what parameter is a string identifying the database feature to list. Most databases
support "databases"; some support "users", "views", and "functions".
For example, this stores a list of available databases in $dbs:
$dbs = $db->getListOf("databases");
Transactions
Some RDBMSs support transactions, in which a series of database changes can be
committed (all applied at once) or rolled back (discarded, with the changes not applied
to the database). For example, when a bank handles a money transfer, the withdrawal
from one account and deposit into another must happen together—neither should
happen without the other, and there should be no time between the two actions.
PEAR DB offers the commit ( ) and rollback( ) methods to help with transactions:
$res = $db->commit( );
$res = $db->rollback( );
If you call commit( ) or rollback( ) on a database that doesn’t support transactions,
the methods return DB_ERROR.
Sample Application
Because web database applications are such a mainstay of web development, we’ve
decided to show you a complete sample application in this chapter. This section
develops a self-maintaining business listing service. Companies add their own records
to the database and pick the category or categories by which they want to be indexed.
202 | Chapter 8: Databases
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