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Data Source Names - PHP

If you're interested in learning how to access databases from PHP, you've come to the right place. This four-part series will focus on the PEAR DB system. This article is excerpted from chapter eight of the book Programming PHP, Second Edition, written by Kevin Tatroe, Rasmus Lerdorf, and Peter MacIntyre (O'Reilly, 2006; ISBN: 0596006810). Copyright © 2006 O'Reilly Media, Inc. All rights reserved. Used with permission from the publisher. Available from booksellers or direct from O'Reilly Media.

  1. Databases and PHP
  2. Relational Databases and SQL
  3. PEAR DB Basics
  4. Data Source Names
By: O'Reilly Media
Rating: starstarstarstarstar / 8
June 14, 2007

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A data source name (DSN) is a string that specifies where the database is located, what kind of database it is, the username and password to use when connecting to the database, and more. The components of a DSN in PEAR are assembled into a URL-like string:

  type(dbsyntax)://username:password@protocol+hostspec/ database

The only mandatory field istype, which specifies the PHP database backend to use. Table 8-1 lists the implemented database types at the time of writing.

Table 8-1. PHP database types

Name Database
Mysql MySQL
mysqli MySQL (for MySQL >= 4.1)
Pgsql PostgreSQL
Ibase InterBase
Msql Mini SQL
Mssql Microsoft SQL Server
oci8 Oracle 7/8/8i
Sybase SyBase
Ifx Informix
Fbsql FrontBase
Dbase DBase
Sqlite SQLite

Theprotocol  is the communication protocol to use. The two common values are"tcp"and"unix,"corresponding to Internet and Unix domain sockets. Not every database backend supports every communications protocol.

These are some sample valid data source names:

  mysql:// librarian:passw0rd@localhost/library

In Example 8-1, we connected to the MySQL databaselibrarywith the usernamelibrarianand passwordpassw0rd.

A common development technique is to store the DSN in a PHP file and include that file in every page that requires database connectivity. Doing this means that if the information changes, you donít have to change every page. In a more sophisticated settings file, you might even switch DSNs based on whether the application is running in development or deployment mode.

Please check back next week for the continuation of this article.

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