ext/pdo_odbc: a bound Unicode (nvarchar) string parameter never matches — WHERE col = ? / WHERE col LIKE ? with a non-ASCII value returns no rows (works correctly with pdo_sqlsrv)

[chep6915]

Description

When a non-ASCII (e.g. CJK) string is bound as a parameter against an nvarchar column on SQL Server via pdo_odbc + Microsoft ODBC Driver 18, the comparison never matches: = ? and LIKE ? both return zero rows, even though the row clearly exists. The same query with the same value works with pdo_sqlsrv.

The parameter appears to be bound as a non-Unicode (SQL_CHAR / ANSI) string rather than SQL_WCHAR, so the bytes sent to the server do not match the nvarchar (UTF-16) column data.

Reproduction (self-contained, no table required)

<?php
$dsn  = "odbc:Driver={ODBC Driver 18 for SQL Server};Server=HOST,1433;Database=DB;Encrypt=no;TrustServerCertificate=yes;";
$pdo  = new PDO($dsn, 'user', 'pass', [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);

// The row value is a literal Unicode string; only the *bound parameter* differs.
$st = $pdo->prepare(
    "SELECT COUNT(*) FROM (SELECT CAST(N'測試中文資料庫' AS nvarchar(100)) AS v) t WHERE v = ?"
);
$st->execute(['測試中文資料庫']);
var_dump($st->fetchColumn());          // expected 1, pdo_odbc returns 0

$st = $pdo->prepare(
    "SELECT COUNT(*) FROM (SELECT CAST(N'測試中文資料庫' AS nvarchar(100)) AS v) t WHERE v LIKE ?"
);
$st->execute(['%中文%']);
var_dump($st->fetchColumn());          // expected 1, pdo_odbc returns 0

Observed vs expected

query	pdo_odbc	pdo_sqlsrv	expected
WHERE v = ? bound '測試中文資料庫'	0	1	1
WHERE v LIKE ? bound '%中文%'	0	1	1

ASCII-only bound parameters match correctly; only non-ASCII (Unicode) bound parameters fail. Literal Unicode in the SQL text (N'...') is handled fine — the problem is specifically the bound parameter encoding.

Environment

• PHP 8.5.8 (NTS, built 2026-07-01).
• unixODBC 2.3.14 (libodbc.2.dylib), pdo_odbc built --with-pdo-odbc=unixODBC.
• Microsoft ODBC Driver 18 for SQL Server, msodbcsql18 18.6.2.1 (libmsodbcsql.18.dylib).
• Microsoft SQL Server 2025 (RTM-CU6, KB5093421) 17.0.4055.5 (X64).
• macOS 26.5.2 (arm64). Not OS-specific — the parameter binding is in ext/pdo_odbc.

PHP Version

PHP 8.5.8 (cli) (built: Jul  1 2026 03:46:27) (NTS)
Copyright (c) The PHP Group
Built by Homebrew
Zend Engine v4.5.8, Copyright (c) Zend Technologies
    with Zend OPcache v8.5.8, Copyright (c), by Zend Technologies

Operating System

macOS 26.5.2 (build 25F84), Apple Silicon / arm64 (Darwin 25.5.0)

[chep6915]

Thanks for the quick fix, and for verifying it on the same unixODBC + ODBC Driver 18 + SQL Server stack — much appreciated!