PDO(PHP Data Objects) is one of main feature of PHP 5.1 to managing databases. It is developed to provide a lightweight interface for different database engines. And one of the very good features of PDO is that it works like a Data Access Layer so that you can use the same function names for all database engines.

PHP Script

<?php
$db_name ='test_db';
$db_host = 'localhost';
$db_user = 'root';
$db_password = 'mypassword';
$dsn = 'mysql:dbname=$db_name;host=$db_host;';
$connectionString = new PDO($dsn, $db_user, $db_password);
?>

The DSN settings for different database engines to connect with PDO. Supported database drivers are as shown below:

PDO_DBLIB for FreeTDS/Microsoft SQL Server/Sybase

mssql:host=localhost;dbname=test_db
sybase:host=localhost;dbname=test_db
dblib:host=localhost;dbname=test_db

PDO_INFORMIX for IBM Informix Dynamic Server

informix:host=host.domain.com;service=9800;database=test_db;
server=ids_server;protocol=onsoctcp;

EnableScrollableCursors=1;

PDO_MYSQL for MySQL 3.x/4.x/5.x

mysql:host=localhost;port=3307;dbname=test_db
mysql:unix_socket=/tmp/mysql.sock;dbname=test_db

PDO_OCI for Oracle Call Interface

oci:mydb
oci:dbname=//localhost:1521/test_db

PDO_ODBC for ODBC v3 (IBM DB2, unixODBC and win32 ODBC)

odbc:test_db
odbc:DRIVER={IBM DB2 ODBC DRIVER};HOSTNAME=localhost;PORT=50000;DATABASE=test_db;
PROTOCOL=TCPIP;UID=db_user_name;PWD=db_password;
odbc:Driver={Microsoft Access Driver (*.mdb)};Dbq=C:db.mdb;Uid=Admin

PDO_PGSQL for PostgreSQL

pgsql:dbname=test_db;user=db_user_name;password=db_password;
host=localhost;port=5432

PDO_SQLITE for SQLite 3 and SQLite 2

sqlite:/opt/databases/mydb.sq3
sqlite::memory:
sqlite2:/opt/databases/mydb.sq2
sqlite2::memory:

PDO_FIREBIRD for Firebird/Interbase 6

firebird:user="db_user_name;Password=db_password;
Database=DATABASE.GDE;DataSource=localhost;Port=3050;