unicode string corruption when using PDO_ODBC with FreeTDS 1.3.6 and MS SQL Server 2016

Description

The following code:

<?php
// setup database connection
$u = getenv('DB_USERNAME');
$p = getenv('DB_PASSWORD');
$dsn = 'odbc:testUTF8';
$db = new \PDO($dsn, $u, $p);
$db->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION);

$constant_tests = [
    "SELECT CAST(0x72006f017e016f007600fd00 AS nvarchar(10)) AS pink_in_czech_binary_encoded_utf16;",
    "SELECT CAST(0x6b26 AS nvarchar(3)) AS Beamed_Eighth_Notes_binary_encoded_utf16;",
    "SELECT NCHAR(0x266b) AS Beamed_Eighth_Notes_nchar;",
    "SELECT N'♫' AS Beamed_Eighth_Notes_unicode_string_constant;",
    "SELECT N'růžový' AS pink_in_czech_unicode_string_constant;",
];
foreach($constant_tests as $t) {
    fwrite(STDERR, "Running query '$t'...\n");
    var_dump($db->query($t, \PDO::FETCH_ASSOC)->fetchAll());
}

Resulted in this output:

Running query 'SELECT CAST(0x72006f017e016f007600fd00 AS nvarchar(10)) AS pink_in_czech_binary_encoded_utf16;'...
array(1) {
  [0]=>
  array(1) {
    ["pink_in_czech_binary_encoded_utf16"]=>
    string(9) "růžový"
  }
}
Running query 'SELECT CAST(0x6b26 AS nvarchar(3)) AS Beamed_Eighth_Notes_binary_encoded_utf16;'...
array(1) {
  [0]=>
  array(1) {
    ["Beamed_Eighth_Notes_binary_encoded_utf16"]=>
    string(3) "♫"
  }
}
Running query 'SELECT NCHAR(0x266b) AS Beamed_Eighth_Notes_nchar;'...
array(1) {
  [0]=>
  array(1) {
    ["Beamed_Eighth_Notes_nchar"]=>
    string(3) "▒▒"
  }
}
Running query 'SELECT N'♫' AS Beamed_Eighth_Notes_unicode_string_constant;'...
array(1) {
  [0]=>
  array(1) {
    ["Beamed_Eighth_Notes_unicode_string_constant"]=>
    string(3) "▒▒"
  }
}
Running query 'SELECT N'růžový' AS pink_in_czech_unicode_string_constant;'...
array(1) {
  [0]=>
  array(1) {
    ["pink_in_czech_unicode_string_constant"]=>
    string(9) "růžo"
  }
}

But I expected this output instead:

Running query 'SELECT CAST(0x72006f017e016f007600fd00 AS nvarchar(10)) AS pink_in_czech_binary_encoded_utf16;'...
array(1) {
  [0]=>
  array(1) {
    ["pink_in_czech_binary_encoded_utf16"]=>
    string(9) "růžový"
  }
}
Running query 'SELECT CAST(0x6b26 AS nvarchar(3)) AS Beamed_Eighth_Notes_binary_encoded_utf16;'...
array(1) {
  [0]=>
  array(1) {
    ["Beamed_Eighth_Notes_binary_encoded_utf16"]=>
    string(3) "♫"
  }
}
Running query 'SELECT NCHAR(0x266b) AS Beamed_Eighth_Notes_nchar;'...
array(1) {
  [0]=>
  array(1) {
    ["Beamed_Eighth_Notes_nchar"]=>
    string(3) "♫"
  }
}
Running query 'SELECT N'♫' AS Beamed_Eighth_Notes_unicode_string_constant;'...
array(1) {
  [0]=>
  array(1) {
    ["Beamed_Eighth_Notes_unicode_string_constant"]=>
    string(3) "♫"
  }
}
Running query 'SELECT N'růžový' AS pink_in_czech_unicode_string_constant;'...
array(1) {
  [0]=>
  array(1) {
    ["pink_in_czech_unicode_string_constant"]=>
    string(9) "růžový"
  }
}

PHP Version

PHP 8.1.7

Operating System

Debian GNU/Linux testing/bookworm/unstable

首先，使用提供的 PHP 脚本、PDO::query() 和 fetchAll()，通过 PDO_ODBC、FreeTDS 1.3.6 和 SQL Server 2016 重现该问题。将 NCHAR 和带 N 前缀的字符串常量返回的值与预期的 Unicode 字符串进行比较；当列出的所有查询都返回未损坏的预期字符时，即表示完成。