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

//SQLite3
sqlite:/opt/databases/mydb.sq3
sqlite::memory:

//SQLite2
sqlite2:/opt/databases/mydb.sq2
sqlite2::memory:

//Microsoft Access
odbc:Driver={Microsoft Access Driver (*.mdb)};Dbq=C:\\db.mdb;Uid=Admin

//Microsoft SQL Server
mssql:host=localhost;dbname=testdb
odbc:Driver={SQL Native Client};Server=250.156.0.1;Database=myDataBase; Uid=userName;Pwd=thePassword;

//PostgreSQL
pgsql:host=localhost;port=5432;dbname=testdb;user=bruce;password=mypass

//Oracle
oci:dbname=mydb  // Connect to a database defined in tnsnames.ora
'oci:dbname=//localhost:1521/mydb'  // Connect using the Oracle Instant Client

//IBM DB2
odbc:DRIVER={IBM DB2 ODBC DRIVER};HOSTNAME=localhost;PORT=50000;DATABASE=SAMPLE;PROTOCOL=TCPIP;UID=db2inst1;PWD=ibmdb2;
ibm:DSN=DB2_9
ibm:DRIVER={IBM DB2 ODBC DRIVER};DATABASE=testdb;HOSTNAME=11.22.33.444;PORT=56789;PROTOCOL=TCPIP;

//Sybase
sybase:host=localhost;dbname=testdb

//DB-lib
dblib:host=localhost;dbname=testdb

//Firebird / Interbase
firebird:dbname=DATABASE.GDE

//4D database
4D:host=localhost;charset=UTF-8

//Informix
informix:DSN=Infdrv33
informix:host=host.domain.com;service=9800;database=common_db;server=ids_server;protocol=onsoctcp;EnableScrollableCursors=1

应用举例：

 $db=new PDO('sqlite:data/mydata.db');
 $q=$db->query("select * from testtable");
 $r=$q->fetchArray();
 var_dump($r);