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PHP Manual [Fleshing out your skeleton]

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PHP Manual || PDO Driver How-To

Major Structures and Attributes

The major structures, pdo_dbh_t and pdo_stmt_t are defined and explained in Appendix A and B respectively. Database and Statement attributes are defined in Appendix C. Error handling is explained in Appendix D.

pdo_SKEL.c: PHP extension glue

function entries

static function_entry pdo_SKEL_functions[] = {

This structure is used to register functions into the global php function namespace. PDO drivers should try to avoid doing this, so it is recommended that you leave this structure initialized to NULL, as shown in the synopsis above.

Module entry

/* {{{ pdo_SKEL_module_entry */
#if ZEND_EXTENSION_API_NO >= 220050617
static zend_module_dep pdo_SKEL_deps[] = {
/* }}} */

zend_module_entry pdo_SKEL_module_entry = {
#if ZEND_EXTENSION_API_NO >= 220050617
/* }}} */


A structure of type zend_module_entry called pdo_SKEL_module_entry must be declared and should include reference to the pdo_SKEL_functions table defined previously.

Standard PHP Module Extension Functions

    return php_pdo_register_driver(&pdo_SKEL_driver);
/* }}} */

This standard PHP extension function should be used to register your driver with the PDO layer. This is done by calling the php_pdo_register_driver() function passing a pointer to a structure of type pdo_driver_t typically named pdo_SKEL_driver. A pdo_driver_t contains a header that is generated using the PDO_DRIVER_HEADER(SKEL) macro and pdo_SKEL_handle_factory() function pointer. The actual function is described during the discussion of the SKEL_dbh.c unit.

    return SUCCESS;
/* }}} */

This standard PHP extension function is used to unregister your driver from the PDO layer. This is done by calling the php_pdo_unregister_driver() function, passing the same pdo_SKEL_driver structure that was passed in the init function above.


This is again a standard PHP extension function. Its purpose is to display information regarding the module when the phpinfo() is called from a script. The convention is to display the version of the module and also what version of the db you are dependent on, along with any other configuration style information that might be relevant.

SKEL_driver.c: Driver implementation

This unit implements all of the database handling methods that support the PDO database handle object. It also contains the error fetching routines. All of these functions will typically need to access the global variable pool. Therefore, it is necessary to use the Zend macro TSRMLS_DC macro at the end of each of these statements. Consult the Zend programmer documentation for more information on this macro.


static int pdo_SKEL_error(pdo_dbh_t *dbh,
  pdo_stmt_t *stmt, const char *file, int line TSRMLS_DC)

The purpose of this function is to be used as a generic error handling function within the driver. It is called by the driver when an error occurs within the driver. If an error occurs that is not related to SQLSTATE, the driver should set either dbh->error_code or stmt->error_code to an SQLSTATE that most closely matches the error or the generic SQLSTATE error HY000. The file pdo_sqlstate.c in the PDO source contains a table of commonly used SQLSTATE codes that the PDO code explicitly recognizes. This setting of the error code should be done prior to calling this function.; This function should set the global pdo_err variable to the error found in either the dbh or the stmt (if the variable stmt is not NULL).


Pointer to the database handle initialized by the handle factory


Pointer to the current statement or NULL. If NULL, the error is derived by error code found in the dbh.


The source file where the error occurred or NULL if not available.


The line number within the source file if available.

If the dbh member methods is NULL (which implies that the error is being raised from within the PDO constructor), this function should call the zend_throw_exception_ex() function otherwise it should return the error code. This function is usually called using a helper macro that customizes the calling sequence for either database handling errors or statement handling errors.

Example #1 Example macros for invoking pdo_SKEL_error

#define pdo_SKEL_drv_error(what) \
    pdo_SKEL_error(dbh, NULL, what, __FILE__, __LINE__ TSRMLS_CC)
#define pdo_SKEL_drv_error(what) \
    pdo_SKEL_error(dbh, NULL, what, __FILE__, __LINE__ TSRMLS_CC)

For more info on error handling, see Error handling.


Despite being documented here, the PDO driver interface does not specify that this function be present; it is merely a convenient way to handle errors, and it just happens to be equally convenient for the majority of database client library APIs to structure your driver implementation in this way.


static int pdo_SKEL_fetch_error_func(pdo_dbh_t *dbh, pdo_stmt_t *stmt,
    zval *info TSRMLS_DC)

The purpose of this function is to obtain additional information about the last error that was triggered. This includes the driver specific error code and a human readable string. It may also include additional information if appropriate. This function is called as a result of the PHP script calling the PDO::errorInfo() method.


Pointer to the database handle initialized by the handle factory


Pointer to the most current statement or NULL. If NULL, the error translated is derived by error code found in the dbh.


A hash table containing error codes and messages.

The error_func should return two pieces of information as successive array elements. The first item is expected to be a numeric error code, the second item is a descriptive string. The best way to set this item is by using add_next_index. Note that the type of the first argument need not be long; use whichever type most closely matches the error code returned by the underlying database API.

/* now add the error information. */
/* These need to be added in a specific order */
add_next_index_long(info, error_code);   /* driver specific error code */
add_next_index_string(info, message, 0); /* readable error message */

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