pdo是php5中新加入的数据库抽象层，为了解决访问不同数据库统一接口的问题。类似于PEAR::DB类和ADODB类的操作，不过它是直接封装再php扩展中，可以自由选择使用。
目前的php5.1beta中已经更好的加入了pdo的支持，我们下看具体帮助。
为了描述清楚，我们把直接把帮助复制过来。
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PDO Functions
The PHP Data Objects (PDO) extension defines a lightweight, consistent interface for accessing databases in PHP. Each database driver that implements the PDO interface can expose database-specific features as regular extension functions. Note that you cannot perform any database functions using the PDO extension by itself; you must use a database-specific PDO driver to access a database server.
安装Windows
Follow the same steps to install and enable the PDO drivers of your choice.
Windows users can download the extension DLL php_pdo.dll as part of the PECL collection binaries from /downloads.php or a more recent version from a PHP 5 PECL Snapshot.
To enable the PDO extension on Windows operating systems, you must add the following line to php.ini: extension=php_pdo.dll
Next, choose the other DB specific DLL files and either use dl() to load them at runtime, or enable them in php.ini below pdo_pdo.dll. For example: extension=php_pdo.dll
extension=php_pdo_firebird.dll
extension=php_pdo_mssql.dll
extension=php_pdo_mysql.dll
extension=php_pdo_oci.dll
extension=php_pdo_oci8.dll
extension=php_pdo_odbc.dll
extension=php_pdo_pgsql.dll
extension=php_pdo_sqlite.dll
These DLL's should exist in the systems extension_dir.
Linux and UNIX
Due to a bug in the pear installer you should install the PDO package manually using the following steps:
Follow the same steps to install and enable the PDO drivers of your choice.
Download the PDO package to your local machine: bash$ wget http://pecl.php.net/get/PDO
Determine your PHP bin directory. If your PHP 5 CLI binary lives at /usr/local/php5/bin/php then the bin dir is /usr/local/php5/bin.
Set your path so that your PHP bin directory is at the front: export PATH="/usr/local/php5/bin:$PATH"
Manually build and install the PDO extension: bash$ tar xzf PDO-0.2.tgz
bash$ cd PDO-0.2
bash$ phpize
bash$ ./configure
bash$ make
bash$ sudo -s
bash# make install
bash# echo extension=pdo.so >> /usr/local/php5/lib/php.ini
PDO DriversThe following drivers currently implement the PDO interface:
Driver nameSupported databasesPDO_DBLIB
FreeTDS / Microsoft SQL Server / Sybase
PDO_FIREBIRD
Firebird/Interbase 6
PDO_MYSQL
MySQL 3.x/4.0
PDO_OCI
Oracle Call Interface
PDO_ODBC
ODBC v3 (IBM DB2 and unixODBC)
PDO_PGSQL
PostgreSQL
PDO_SQLITE
SQLite 3.x
预定义类PDORepresents a connection between PHP and a database server.
构造函数
PDO - constructs a new PDO object
方法
beginTransaction - begins a transaction
commit - commits a transaction
exec - issues an SQL statement and returns the number of affected rows
errorCode - retrieves an error code, if any, from the database
errorInfo - retrieves an array of error information, if any, from the database
getAttribute - retrieves a database connection attribute
lastInsertId - retrieves the value of the last row that was inserted into a table
prepare - prepares an SQL statement for execution
query - issues an SQL statement and returns a result set
quote - returns a quoted version of a string for use in SQL statements
rollBack - roll back a transaction
setAttribute - sets a database connection attribute
PDOStatementRepresents a prepared statement and, after the statement is executed, an associated result set.
方法
bindColumn - binds a PHP variable to an output column in a result set
bindParam - binds a PHP variable to a parameter in the prepared statement
columnCount - returns the number of columns in the result set
errorCode - retrieves an error code, if any, from the statement
errorInfo - retrieves an array of error information, if any, from the statement
execute - executes a prepared statement
fetch - fetches a row from a result set
fetchAll - fetches an array containing all of the rows from a result set
fetchSingle - returns the data from the first column in a result set
getAttribute - retrieves a PDOStatement attribute
getColumnMeta - retrieves metadata for a column in the result set
nextRowset - retrieves the next rowset (result set)
rowCount - returns the number of rows that were affected by the execution of an SQL statement
setAttribute - sets a PDOStatement attribute
setFetchMode - sets the fetch mode for a PDOStatement
我们看第一组方法是查询的部分方法，第二组方法是获取数据集的方法。
我们看如何连接一个数据库。我们使用pdo的构造函数来连接数据库：
PDO::__construct(no version information, might be only in CVS)
PDO::__construct -- Creates a PDO instance representing a connection to a database
说明PDO PDO::__construct ( string dsn [, string username [, string password [, array driver_options]]] )
Creates a PDO instance to represent a connection to the requested database.
参数
dsn The Data Source Name, or DSN, contains the information required to connect to the database.
In general, a DSN consists of the PDO driver name, followed by a colon, followed by the PDO driver-specific connection syntax. Examples of each driver are given below:
PDO_DBLIB The DSN prefix is either sybase: or mssql: depending on which libraries it was linked against during compilation.
sybase:host=localhost; dbname=testdb
mssql:host=localhost; dbname=testdb
PDO_FIREBIRD firebird:User=john;Password=mypass;Database=DATABASE.GDE;DataSource=localhost;Port=3050
PDO_MYSQL mysql:host=localhost;dbname=testdb
PDO_OCI To connect via tnsnames.ora, use:
oci:mydb
If using instantclient, use:
oci:dbname=//localhost:1521/testdb
PDO_ODBC odbc:DSN=SAMPLE;UID=john;PWD=mypass
DSN=SAMPLE refers to the SAMPLE data source configured in the ODBC driver manager.
PDO_PGSQL pgsql:host=localhost port=5432 dbname=testdb user=john password=mypass
Note, by passing user and password in the DSN, the username and password parameters become optional. If specified, they are glued to the end of the connection string.
PDO_SQLITE sqlite:/path/to/database
To create a database in memory, use:
sqlite::memory:
The dsn parameter supports three different methods of specifying the arguments required to create a database connection:
Driver invocation dsn contains the full DSN.
URI invocation dsn consists of uri: followed by a URI that defines the location of a file containing the DSN string. The URI can specify a local file or a remote URL.
uri:file:///path/to/dsnfile
Aliasing dsn consists of a name name that maps to pdo.dsn.name in php.ini defining the DSN string.
注: The alias must be defined in php.ini, and not .htaccess or httpd.conf
username The user name for the DSN string. This parameter is optional for some PDO drivers.
password The password for the DSN string. This parameter is optional for some PDO drivers.
driver_options A key=>value array of driver-specific connection options.
返回值Returns a PDO object on success.
异常PDO::construct() throws a PDOException if the attempt to connect to the requested database fails.
例例子 1. Create a PDO instance via driver invocation
<?php
// Connect to an ODBC database using driver invocation
$dsn = 'mysql:dbname=testdb;host=127.0.0.1';
$user = 'dbuser';
$password = 'dbpass';
try {
$dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
?>
例子 2. Create a PDO instance via URI invocation
The following example assumes that the file /usr/local/dbconnect exists with file permissions that enable PHP to read the file. The file contains the PDO DSN to connect to a DB2 database through the PDO_ODBC driver:
odbc:DSN=SAMPLE;UID=john;PWD=mypass
The PHP script can then create a database connection by simply passing the uri: parameter and pointing to the file URI:
<?php
// Connect to an ODBC database using driver invocation
$dsn = 'uri:file:///usr/local/dbconnect';
$user = '';
$password = '';
try {
$dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
?>
例子 3. Create a PDO instance using an alias
The following example assumes that php.ini contains the following entry to enable a connection to a MySQL database using only the alias mydb: [PDO]
pdo.dsn.mydb="mysql:dbname=testdb;host=localhost"
<?php
// Connect to an ODBC database using an alias
$dsn = 'mydb';
$user = '';
$password = '';
try {
$dbh = new PDO($dsn, $user, $password);
}catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
?>
其他的方法请参考手册：http://cn.php.net/pdo
说明：以上内容基本来源于手册，请自行参考手册获取更详细的内容。