ODBC and DB2 Functions (PDO_ODBC)

Einführung

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, and is the recommended driver for connecting to Microsoft SQL Server databases.

Installation

PDO_ODBC on UNIX systems

  1. As of PHP 5.1, PDO_ODBC is included in the PHP source. You can compile the PDO_ODBC extension as either a static or shared module using the following configure commands.

    ibm_db2

    ./configure --with-pdo-odbc=ibm-db2,/opt/IBM/db2/V8.1/
    To build PDO_ODBC with the ibm-db2 flavour, you have to have previously installed the DB2 application development headers on the same machine on which you are compiling PDO_ODBC. The DB2 application development headers are an installable option in the DB2 servers, and are also available as part of the DB2 Application Development Client freely available for download from the IBM developerWorks » website.

    If you do not supply a location for the DB2 libraries and headers to the configure command, PDO_ODBC defaults to /home/db2inst1/sqllib.

    unixODBC

    ./configure --with-pdo-odbc=unixODBC,/usr/local
    If you do not supply a location for the unixODBC libraries and headers to the configure command, PDO_ODBC defaults to /usr/local.

    generic
    ./configure --with-pdo-odbc=generic,/usr/local,libname,ldflags,cflags

Vordefinierte Konstanten

Die folgenden Konstanten werden vom Treiber definiert und sind nur verfügbar, wenn die Extension entweder in PHP einkompiliert oder dynamisch zur Laufzeit geladen wurde. Weiterhin sind diese Konstanten treiberspezifisch und sollten nur mit diesem Treiber benutzt werden. MySQL-spezifische Attribute mit dem PostgreSQL Treiber zu nutzen, kann zu unerwarteten Ergebnissen führen. Kann Ihr Code mit verschiedenen Treibern arbeiten, so können Sie PDO::getAttribute() benutzen, um mit PDO_ATTR_DRIVER_NAME den aktuellen Treiber zu ermitteln.

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), no character encoding conversion is done.

Laufzeit-Konfiguration

Das Verhalten dieser Funktionen wird durch Einstellungen in der php.ini beeinflusst.

PDO_ODBC Configuration Options
Name Standard Veränderbar Changelog
pdo_odbc.connection_pooling "strict" PHP_INI_ALL Available since PHP 5.1.0.
pdo_odbc.db2_instance_name NULL PHP_INI_SYSTEM Available since PHP 5.1.1. Dieses veraltete Feature wird in der Zukunft sicherlich entfernt.
Weitere Details und die Definitionen der PHP_INI_*-Konstanten finden Sie im Wo Konfigurationseinstellungen gesetzt werden können.

Hier eine kurze Erklärung der Konfigurationsoptionen:

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.

Warnung

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

Tipp

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.

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