• Version: 0.1
• Date: 2017-02-16
• Author: Adam Baratz adambaratz@php.net
• Status: Under Discussion
• First Published at: https://wiki.php.net/rfc/extended-string-types-for-pdo

MySQL and Microsoft SQL Server define special column types for storing Unicode strings. There is a different format for literals of this type.

When using emulated prepared statements -- the default behavior for pdo_mysql, the only one for pdo_dblib -- it's not possible to quote parameters using this format. By not doing this, queries become more expensive because of an implicit cast.

There aren't many pdo_dblib users who comment regularly on the internals list, but the presence of a feature request and a pull request suggests that this is an impactful omission.

Three constants would be added to the pdo extension:

1. PDO::PARAM_STR_UNICODE. A new type, to be applied as a bitwise-OR to PDO::PARAM_STR. It would indicate that the value should be quoted with the N-prefix.
2. PDO::ATTR_UNICODE_STRINGS. This bool driver attribute would indicate whether all PDO::PARAM_STR values should be treated like PDO::PARAM_STR | PDO::PARAM_STR_UNICODE by default.
3. PDO::PARAM_STR_ASCII. A new type, to be applied as a bitwise-OR to PDO::PARAM_STR. It would indicate that the value should be quoted without the N-prefix. This would be intended to be used as an exception for when the PDO::ATTR_UNICODE_STRINGS attribute is set to true.

Since this functionality would be opt-in, existing code would continue to work as it does. The bitmasked values would be ignored by other drivers, or pdo_mysql toggling off prepared statement emulation, so the portability valued for PDO code would be preserved.

Drivers outside of php-src might have to be modified if they make assumptions about the structure of enum pdo_param_type. They would have to be rebuilt since the PDO_DRIVER_API macro would be updated.

Next PHP 7.x.

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