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Before you can use the PDO_ODBC extension in any given version of PHP, you must first disable the odbc, pdo_ibm, and ibm_db2 extensions in that version of PHP. To do it, go into the Zend Server User Interface. Navigate to PHP -> phpinfo(), and make a note of the version currently in use. If you want to use a different version of PHP, please change it at this time.
Important note: The unixODBC driver creates a linking failure in PHP if any extension using the old SQL-CLI (libdb400.a) driver is also loaded. This is because there is a naming conflict between the drivers that will cause the linked SQLSetEnvAttrr to be called from the wrong driver, and PHP will fail to start. So, before you can enable the PDO_ODBC extension, you need to disable the odbc, pdo_ibm, and ibm_db2 extensions. You need to disable the odbc extension because it uses SQL-CLI instead of unixODBC. This was done to maintain backward compatibility with older versions of Zend Server.
Next, navigate to PHP -> Extensions, and select all three of these extensions: ibm_db2, odbc, and pdo_ibm (you can skip any if they are already off, but they are usually all on by default). With the extensions selected, click the Disable button at the top of the table. Restart Apache for the change to take effect, by using the restart icon (circular arrow at top right of the page, should be orange because restart is due).
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