Request for Comments: PDO version 1 improvements

• Version: pre alpha 0.1
• Date: 2008-03-06
• Author: Lukas Smith smith@pooteeweet.org
• Status: Draft (Inactive)

This RFC aims to collect a set of ideas to improve PDO version 1. These ideas will hopefully end up in a set of concret feature requests and patches.

PDO is a thin layer above native RDBMS interfaces. As such its focused on providing a unified API on the PHP level without getting too much into SQL abstraction. PDO provides a framework to make the development of RDBMS specific drivers for PDO easier.

PDO has become the de-facto standard for the development of PHP libraries that interact with RDBMS. As such developers have come to expect that PDO minimizes any portability differences to a minimum, while accepting that PDO will not solve most issues in the differences of the actual SQL syntax.

A lot in PDO can be fixed without a new major version.

• Convenience features
  • Add a common syntax to specify the DSN along the lines of the PEAR DSN format
  • Add ability to generate a properly quoted comma separated list to be embedded in a query inside an IN() clause (see implodeArray())
• Higher level emulation features
  • Fix differences in behavior for data fetches (possibly add a compatibility mode in order to maintain BC)
  • Add ability to manage connection session aspects like charset/collation, locale (datetime/currency format)
  • Add limited sub select emulation (see subSelect())
  • A class for administrative functionality which can come in handy for projects like phpMyAdmin. (possibly partially in userland)
  • Nested transaction emulation via SAVEPOINTs
  • Emulate scrollable cursors via buffered result sets
• Prepared statements
  • Fix differences in when bind/prepare issues an exception for an invalid bound value/parameter.
  • Add ability to bind short binary values
  • Improve the prepared statement emulation parser to better deal with quoted strings that contain things that look like a placeholder
  • Make it possible to disable parsing and rewriting of placeholders and require the use of the given native syntax (:name, $name, ? etc.)
  • Fix the problems with ODBC prepared statements when executing procedures on all platforms.
  • Add support for PDO::PARAM_CLOB and generally work harder on making the LOB behavior more similar across the drivers (see Bug 7943)
  • Add support for datatypes like float and datetime/timestamp
  • Do not force the use of prepared statements internally for simple queries without any parameters
  • Optionally only use native prepared statement for SQL injection protection, but leverage the ability of some RDBMS to pass the [http://pooteeweet.org/blog/1233 statement and the values in a single call]
• Improve documentation
• Add support of multiple resultsets for mssql and odbc on all platforms.
• Add ability to retrieve the parameters set in the constructor (like DSN etc.)
• Add ability to determine the state of the connection/transactions (as well as the ability to reconnect)
• Make sure PDO classes implement interfaces so that frameworks can use it as a generic data access interface and implement native driver versions of it if needed (esp. PDOStatement).
• OCI8 has some persistent connection tuning parameters like timeout, max_connections, ... Make that generic and consistent in PDO.
• Improved Quoting
  • Consider having an attribute that sets quoting style + maybe even allow for a callback for quoting.
  • Making quoting function aware of encoding in PDO (add quoting for identifier & value)
• Improved error handling and debugging
  • Add some better debugging hooks (like a way to get the last submitted statement, this is important especially when PDO does some rewriting like with prepared statements)
  • For consistency it would be good to clear errors on every call and provide facility to expose multiple notices/errors that have occurred within a transaction
  • Throw an exception if a fetch method is call on a statement that has not been executed at least once
  • Expand support for SQLSTATE error codes to ensure that all drivers return more or less compatible error codes
• Full blown Metadata APIs ala JDBC (important for higher-level DB layers). (possibly partially in userland)
• Test suite which DB driver authors can use for compliance testing.

• Add support for “IN (?)” type prepared placeholders. <= native prepared statement mandate that all placeholders only handle a single scalar value

• http://php.net/pdo (userland manual)
• http://php.net/internals2.pdo (internals manual)
• http://wiki.php.net/rfc/pdonotices (rfc about database notices which can be handled by PDO)

• http://pooteeweet.org/blog/1048