ODBC and DB2 Functions (PDO_ODBC)

Introduction

PDO_ODBC is a driver that implements the PHP Data Objects (PDO) interface to enable access from PHP to databases through ODBC drivers or through the IBM DB2 Call Level Interface (DB2 CLI) library. PDO_ODBC currently supports three different "flavours" of database drivers:

ibm-db2

Supports access to IBM DB2 Universal Database, Cloudscape, and Apache Derby servers through the free DB2 express-C client.

unixODBC

Supports access to database servers through the unixODBC driver manager and the database's own ODBC drivers.

generic

Offers a compile option for ODBC driver managers that are not explicitly supported by PDO_ODBC.

On Windows, php_pdo_odbc.dll has to be enabled as extension in php.ini. It is linked against the Windows ODBC Driver Manager so that PHP can connect to any database cataloged as a System DSN.

Installation

Predefined Constants

The constants below are defined by this driver, and will only be available when the extension has been either compiled into PHP or dynamically loaded at runtime. In addition, these driver-specific constants should only be used if you are using this driver. Using driver-specific attributes with another driver may result in unexpected behaviour. PDO::getAttribute() may be used to obtain the PDO::ATTR_DRIVER_NAME attribute to check the driver, if your code can run against multiple drivers.

PDO::ODBC_ATTR_USE_CURSOR_LIBRARY (int)

This option controls whether the ODBC cursor library is used. The ODBC cursor library supports some advanced ODBC features (e.g. block scrollable cursors), which may not be implemented by the driver. The following values are supported:

• PDO::ODBC_SQL_USE_IF_NEEDED (the default): use the ODBC cursor library when needed.

• PDO::ODBC_SQL_USE_DRIVER: never use the ODBC cursor library.

• PDO::ODBC_SQL_USE_ODBC: always use the ODBC cursor library.

PDO::ODBC_ATTR_ASSUME_UTF8 (bool)

Windows only. If true, UTF-16 encoded character data (CHAR, VARCHAR and LONGVARCHAR) is converted to UTF-8 when reading from or writing data to the database. If false (the default), character encoding conversion may be done by the driver.

Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

Here's a short explanation of the configuration directives.

pdo_odbc.connection_pooling string

Whether to pool ODBC connections. Can be one of "strict", "relaxed" or "off" (equals to ""). The parameter describes how strict the connection manager should be when matching connection parameters to existing pooled connections. strict is the recommend default, and will result in the use of cached connections only when all the connection parameters match exactly. relaxed will result in the use of cached connections when similar connection parameters are used. This can result in increased use of the cache, at the risk of bleeding connection information between (for example) virtual hosts.

This setting can only be changed from the php.ini file, and affects the entire process; any other modules loaded into the process that use the same ODBC libraries will be affected too, including the Unified ODBC extension.

Warning

relaxed matching should not be used on a shared server, for security reasons.

Tip

Leave this setting at the default strict setting unless you have good reason to change it.

pdo_odbc.db2_instance_name string

If you compile PDO_ODBC using the db2 flavour, this setting sets the value of the DB2INSTANCE environment variable on Linux and UNIX operating systems to the specified name of the DB2 instance. This enables PDO_ODBC to resolve the location of the DB2 libraries and make cataloged connections to DB2 databases.

This setting can only be changed from the php.ini file, and affects the entire process; any other modules loaded into the process that use the same ODBC libraries will be affected too, including the Unified ODBC extension.

This setting has no effect on Windows.