PDO PostreSQL - parser is broken for `'...\'`

Description

The following code:

<?php

$pdo = new PDO('pgsql:host=127.0.0.1;dbname=xxx', 'user', 'pass');

$sql = <<<'EOF'
    select :a x, '\' x2
    EOF;
$statement = $pdo->prepare($sql);
$statement->bindValue('a', 'va');

$statement->execute();
$res = $statement->fetchAll(PDO::FETCH_ASSOC);
var_dump($res);

$sql = <<<'EOF'
    select :a x, '\' x2, :b y, '\' y2
    EOF;
$statement = $pdo->prepare($sql);
$statement->bindValue('a', 'va');
$statement->bindValue('b', 'vb');

$statement->execute();
$res = $statement->fetchAll(PDO::FETCH_ASSOC);
var_dump($res);

Resulted in this output:

array(1) {
  [0]=>
  array(2) {
    ["x"]=>
    string(2) "va"
    ["x2"]=>
    string(1) "\"
  }
}

Warning: PDOStatement::bindValue(): SQLSTATE[HY093]: Invalid parameter number: :b in C:\...\repro.php on line 20
array(0) {
}

But I expected this output instead:

array(1) {
  [0]=>
  array(2) {
    ["x"]=>
    string(2) "va"
    ["x2"]=>
    string(1) "\"
  }
}
array(1) {
  [0]=>
  array(4) {
    ["x"]=>
    string(2) "va"
    ["x2"]=>
    string(1) "\"
    ["y"]=>
    string(2) "vb"
    ["y2"]=>
    string(1) "\"
  }
}

'\' is causing the issue - but it is absolutely correct string syntax.

Identifier escaping ("\") is broken as well.

It seems php-src parses the SQL using the old mode (default until PostgreSQL 9.1) - https://www.postgresql.org/docs/current/runtime-config-compatible.html#GUC-STANDARD-CONFORMING-STRINGS.

PHP Version

any (tested 7.4 and 8.3)

Operating System

any (tested Windows and linux)