pdo_dblib throws incorrect PDOException for UNIQUE constraint violation

Description

The following code:

<?php
$pdo = new PDO("dblib:host=myserver.example.org");
$pdo->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION);
$pdo->exec('DROP TABLE IF EXISTS tempdb.dbo.myTable;');
$pdo->exec('CREATE TABLE tempdb.dbo.myTable (id int UNIQUE);');
$i = $pdo->prepare("INSERT INTO tempdb.dbo.myTable (id) VALUES (:id);");
$i->execute([':id' => 1]);
$i->execute([':id' => 1]);  // should throw exception for UNIQUE violation
exit(0);

Resulted in this output with a PDOException thrown having the SQLSTATE error code set to HY000 [General error]:

PHP Fatal error:  Uncaught PDOException: SQLSTATE[HY000]: General error: 20018 Violation of UNIQUE KEY constraint 'UQ__myTable__3213E83EB59C83C0'. Cannot insert duplicate key in object 'dbo.myTable'. The duplicate key value is (1). [20018] (severity 14) [INSERT INTO tempdb.dbo.myTable (id) VALUES ('1');] in ~/mybug.php:9
Stack trace:
#0 ~/mybug.php(9): PDOStatement->execute()
#1 {main}
  thrown in ~/mybug.php on line 9

But I expected this output instead with a PDOException thrown having the SQLSTATE error code set to 23000 [Integrity constraint violation]):

PHP Fatal error:  Uncaught PDOException: SQLSTATE[23000]: Integrity constraint violation: Violation of UNIQUE KEY constraint 'UQ__myTable__3213E83EB59C83C0'. Cannot insert duplicate key in object 'dbo.myTable'. The duplicate key value is (1). (severity 14) [INSERT INTO tempdb.dbo.myTable (id) VALUES ('1');] in ~/mybug.php:9
Stack trace:
#0 ~/mybug.php(9): PDOStatement->execute()
#1 {main}
  thrown in ~/mybug.php on line 9

Ref for SQLSTATEs: https://docs.microsoft.com/en-us/sql/odbc/reference/appendixes/appendix-a-odbc-error-codes

Note that if you use tsql from freetds/libtds directly (without pdo_dblib), you get this output:

$ tsql -H myserver.example.org -p 1433
locale is "en_US.UTF-8"
locale charset is "UTF-8"
using default charset "UTF-8"
1> DROP TABLE IF EXISTS tempdb.dbo.myTable;
2> CREATE TABLE tempdb.dbo.myTable (id int UNIQUE);
3> INSERT INTO tempdb.dbo.myTable (id) VALUES (1);
4> GO
1> INSERT INTO tempdb.dbo.myTable (id) VALUES (1);
2> GO
Msg 2627 (severity 14, state 1) from MYSERVER Line 1:
        "Violation of UNIQUE KEY constraint 'UQ__myTable__3213E83E6D65FB8A'. Cannot insert duplicate key in object 'dbo.myTable'. The duplicate key value is (1)."
Msg 3621 (severity 0, state 0) from MYSERVER Line 1:
        "The statement has been terminated."
1> quit
$

PHP Version

PHP 8.1.7

Operating System

Debian unstable/testing/bookworm

Start by reproducing the duplicate-key case with pdo_dblib, FreeTDS, and SQL Server using the PHP example, then compare its SQLSTATE with the direct tsql output. Trace how the PDO driver handles the reported database error; done means the UNIQUE violation is exposed as SQLSTATE 23000 while preserving the existing error details.