Table of Contents

Thoughts and ideas about improving PDO. Wez's PDOv1 spec could be useful: http://www.php.net/~wez/pdo/pdo-spec.html

Relevant RFC

Questions

PDO Bugs / PDO2 Improvements

PDO

Documentation

Parameter binding & explicit data type set

fetchObject

Unified API meta data access

see http://news.php.net/php.pdo/233

Asynchronous requests

see http://news.php.net/php.pdo/268

For features not yet finalized: see http://news.php.net/php.pdo/286 PDO_Driver::getNative()::asyncQuery();

Most drivers allow some kind of async query except MySQL, additional connections could be created to allow concurrent queries.

see http://news.php.net/php.pdo/330

PDO Persistent Connections

see http://news.php.net/php.pdo/318 see http://news.php.net/php.pdo/319

PDO2

fetchAll

XML Support

see http://news.php.net/php.pdo/233

Transaction

PDO transaction object see http://news.php.net/php.pdo/322

Possible problems:

Parameter Binding without Preparing

Allow prepareless binding of parameters for queries, like PostgreSQL PQexecParams.

PDO Binding behaviour (5.3)

MySQL SQLite Firebird ODBC PostgreSQL
PDO_PARAM_STR zval type convert_to_string/null zval type/null convert_to_string/ convert_to_string
PDO_PARAM_INT convert_to_long/null convert_to_string convert_to_string
PDO_PARAM_BOOL convert_to_long/null convert_to_string convert_to_string
PDO_PARAM_NULL always null always null if zval IS_NULL
PDO_PARAM_LOB “ * convert_to_string*/null convert_to_string* convert_to_string *
stream support * Supports streams * Supports streams * Supports streams * Supports streams

mysql:

firebird: Check if field allows null, for empty strings and field type is SQL_SHORT, SQL_LONG, SQL_INT64, SQL_FLOAT, SQL_DOUBLE, SQL_TIMESTAMP, SQL_TYPE_DATE, SQL_TYPE_TIME null is assumed as input

odbc: zval == IS_NULL or PDO_PARAM_NULL => always SQL_NULL_DATA

PostgreSQL: zval == IS_BOOL => always bool except if set to PDO_PARAM_NULL (Does reference check, and zval separation before convert_to_string if it isn't a reference)

PDO Binding behaviour RFC

for all bindValue/bindParam/execute input

Why do we need improvements to binding?

Currently has no standard or agreement how parameters like PDO_PARAM_BOOL should be handled on the user side or the internal PDO drivers. There are even disagreements between PDOs code comment, explaining PDO_PARAM_INT is the internal PHP type, and the manual telling us it's the database native type. The result is there is no agreement how even simple parameters should be bound properly and so each driver does it's own guessing how parameters are handled.

The current situation

There are two basic categories how currently driver handle bindings: Trying to guess the right meaning by the zval type (even if PDO is told to use a certain type) Or try to convert it to string and let the database handle most stuff.

So each driver needs some special care when binding, generally for PDO mysql you need to cast to the right type as setting the binding type constant has no affect. The PDO core already convert doubles to string in the pdo_stmt.c really_register_bound_param function. The current code may or may not separate the zval, so the contents of the variable may change after a successful binding or executing of a statement.

Proposal

PDO should enforce the zval type in really_register_bound_param so drivers will get a pre-filtered parameters

This would mean: PDO_PARAM_* will map to internal PHP types, as the code comments in the enum pdo_param_type already tells us. PDO_PARAM_ZVAL will be introduced to user space to let zvals pass directly.

If the zval type isn't right, PDO should do a zval separation before converting so no user space variables will be altered.

PDO_PARAM_DOUBLE should be introduced later to complete the current support.

Problems

PostgreSQL: Currently it's possible to pass a string like “NO” with PDO::PARAM_BOOL, the string contents will be evaluated by the pdo driver, so “no” gets the equivalent of zend false.

As soon as PDO Core enforces types and simply use convert_to_boolean bindValue(':foo', 'NO', PDO::PARAM_BOOL) would result into zend true, passed to pdo postgre it would store true!

But as bindValue defaults to PDO::PARAM_STR and so currently with PostgreSQL you don't need PDO::PARAM_BOOL the impact on current software shouldn't be big.

Workarounds

Possible workaround: A special convert_to_boolean function to support SQL FALSE and NO as zend false, however this would be unnatural to PHP core.

Matrix

zval/PDO PDO_PARAM_NULL PDO_PARAM_BOOL PDO_PARAM_INT PDO_PARAM_STR PDO_PARAM_LOB PDO_PARAM_AUTO (new)
IS_NULL - no convert - SQL_NULL SQL_NULL SQL_NULL SQL_NULL SQL_NULL
IS_LONG SQL_NULL convert_to_boolean - no convert - convert_to_string convert_to_string zval type
IS_DOUBLE SQL_NULL convert_to_boolean - no convert - convert_to_string convert_to_string zval type
IS_BOOL SQL_NULL - no convert - convert_to_long convert_to_string convert_to_string zval type
IS_ARRAY Exception Exception (2) Exception (2) Exception (2) Exception Exception/zval type(2)
IS_OBJECT Exception Exception (1) Exception (1) _toString or Exception _toString or Exception Exception
IS_STRING empty => Null Exception convert_numeric or Exception - no convert - - no convert - zval type
IS_RESSOURCE Exception Exception Exception? convert_to_string(3) convert_to_string(3) convert_to_string(3)

(1) there is no _toType yet

(2) An Array of PDO_PARAM_AUTO could be added for Databases allowing Arrays? PostgreSQL?

(3) Allowing streams

For compatibility the execute() function could be changed to PDO_PARAM_ZVAL for less BC breaks on certain drivers.