You may receive this error when testing a PDO-ODBC connection:
"The specified DSN contains an architecture mismatch between the Driver and Application"
My environment was Windows 7 (64 bit), MySQL ODBC drivers (64 bit), Apache 2.2.17 (32 bit), PHP 5.3.5 (32 bit).
If you are like me, you were testing the PDO-ODBC connection because the native database drivers were not visible to PHP. Furthermore, the MySQL 32 bit drivers did not work in my environment.
Solution: Your environment has to be 64 bit all the way through.
Install 64 bit versions of Apache and PHP. They are not available from official sources. However, kind people have compiled some and made them available for download.
As a bonus, the native database drivers suddenly showed up enabled.
PDO and the PDO_SQLITE driver is enabled by default as of PHP 5.1.0. You may need to enable the PDO driver for your database of choice; consult the documentation for database-specific PDO drivers to find out more about that.
When building PDO as a shared extension (not recommended) then all PDO drivers must be loaded after PDO itself.
When installing PDO as a shared module, the php.ini file needs to be updated so that the PDO extension will be loaded automatically when PHP runs. You will also need to enable any database specific drivers there too; make sure that they are listed after the pdo.so line, as PDO must be initialized before the database-specific extensions can be loaded. If you built PDO and the database-specific extensions statically, you can skip this step.
PDO and all the major drivers ship with PHP as shared extensions, and simply need to be activated by editing the php.ini file:
This step is not necessary for PHP 5.3 and above, as a DLL is no longer required for PDO.
Next, choose the other database-specific DLL files and either use dl() to load them at runtime, or enable them in php.ini below php_pdo.dll. For example:
extension=php_pdo.dll extension=php_pdo_firebird.dll extension=php_pdo_informix.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 DLLs should exist in the system's extension_dir.
Remember that after making changes to your php.ini file you will need to restart PHP for your new configuration directives to take effect.
This page states
"You may need to enable the PDO driver for your database of choice; consult the documentation for [database-specific PDO drivers] to find out more about that."
With the term "database-specific PDO drivers" being a link to this information. However you will no find this information on that or any of the pages that it in turn links to.
The appropriate config options seems to be only available by running ./config --help from the source directory after running autoconf.
Here is the related output from running that command:
--with-pdo-dblib[=DIR] PDO: DBLIB-DB support. DIR is the FreeTDS home directory
--with-pdo-firebird[=DIR] PDO: Firebird support. DIR is the Firebird base
install directory [/opt/firebird]
--with-pdo-mysql[=DIR] PDO: MySQL support. DIR is the MySQL base directoy
If mysqlnd is passed as DIR, the MySQL native
native driver will be used [/usr/local]
--with-zlib-dir[=DIR] PDO_MySQL: Set the path to libz install prefix
--with-pdo-oci[=DIR] PDO: Oracle OCI support. DIR defaults to $ORACLE_HOME.
for an Oracle Instant Client SDK.
For Linux with 10.2.0.3 RPMs (for example) use:
PDO: Support for 'flavour' ODBC driver.
include and lib dirs are looked for under 'dir'.
'flavour' can be one of: ibm-db2, iODBC, unixODBC, generic
If ',dir' part is omitted, default for the flavour
you have selected will used. e.g.:
will check for unixODBC under /usr/local. You may attempt
to use an otherwise unsupported driver using the "generic"
flavour. The syntax for generic ODBC support is:
When build as shared the extension filename is always pdo_odbc.so
--with-pdo-pgsql[=DIR] PDO: PostgreSQL support. DIR is the PostgreSQL base
install directory or the path to pg_config
PDO: sqlite 3 support. DIR is the sqlite base
install directory [BUNDLED]
So if you wish for instance to install the PostgreSQL PDO driver, then you should add the --with-pdo-pgsql config option before compiling PHP. I may have made mistakes in my explination, however it appears to work and was my best guess given the absence of the mentioned documentation.