The source directory for a typical PDO driver is laid out as follows, where
SKEL represents a shortened form of the name of the
database that the driver is going to connect to. Even though SKEL is
presented here in uppercase (for clarity), the convention is to use
lowercase characters.
The easiest way to get started is to use the ext_skel
shell script found in the PHP build tree in the ext
directory. This will build a skeleton directory containing a lot of the
files listed above. It can be build by executing the following command from
within the ext directory:
./ext_skel --extname=pdo_SKEL
This will generate a directory called pdo_SKEL containing the
skeleton files that you can then modify. This directory should then be
moved out of the php extension directory . PDO is a PECL extension and
should not be included in the standard extension directory. As long as you
have PHP and PDO installed, you should be able to build from any directory.
The header file config.h is generated by the configure process for the
platform for the which the driver is being built. If this header is
present, the HAVE_CONFIG_H compiler variable is set. This variable should
be tested for and if set, the file config.h should be included in the
compilation unit.
The following standard public PDO header files are also included in each
source module:
pdo/php_pdo.h
This header file contains definitions of the initialization and shutdown
functions in the main driver as well as definitions of global PDO
variables.
pdo/php_pdo_driver.h
This header contains the types and API contracts that are used to write
a PDO driver. It also contains method signature for calling back into
the PDO layer and registering/unregistering your driver with
PDO. Most importantly, this header file contains the type
definitions for PDO database handles and statements. The two main
structures a driver has to deal with, pdo_dbh_t and pdo_stmt_t, are
described in more detail in Appendix A and B.
The typical PDO driver has two header files that are specific to the
database implementation. This does not preclude the use of more depending
on the implementation. The following two headers are, by convention,
standard:
php_pdo_SKEL.h
This header file is virtually an exact duplicate in functionality
and content of the previously defined pdo/php_pdo.h that has been
specifically tailored for your database. If your driver requires
the use of global variables they should be defined using the
ZEND_BEGIN_MODULE_GLOBALS and ZEND_END_MODULE_GLOBALS macros.
Macros are then used to access these variables. This macro is
usually named PDO_SKEL_G(v) where v is global variable to be
accessed. Consult the Zend programmer documentation for more
information.
php_pdo_SKEL_int.h
This header file typically contains type definitions and function
declarations specific to the driver implementation. It also should
contain the db specific definitions of a pdo_SKEL_handle and
pdo_SKEL_stmt structures. These are the names of the private
data structures that are then referenced by the driver_data members
of the handle and statement structures.
