Description:
------------
PDOStatement failed to bindValue with standard_conforming_strings=on. Setting PDO::ATTR_EMULATE_PREPARES true/false is irrelevant.

Seems to me as a bug during `?` replacing by the `$1` or by the value in emulated prepares mode. In the PostgreSQL log is message:

ERROR:  syntax error at or near "," at character 51
STATEMENT:  INSERT INTO test (col1, col2, col3) VALUES ('\', ?, ' ')

Test script:
---------------
$pdo = new PDO('pgsql:host=localhost;dbname=test', 'test', 'test');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$pdo->query('SET standard_conforming_strings TO on');

$stmt = $pdo->prepare("INSERT INTO test (col1, col2, col3) VALUES ('\\', ?, ' ')");
$stmt->bindValue(1, 'x', PDO::PARAM_STR);
$stmt->execute();

# following are successful
$stmt = $pdo->prepare("INSERT INTO test (col1, col2, col3) VALUES ('\\ ', ?, ' ')");
$stmt = $pdo->prepare("INSERT INTO test (col1, col2) VALUES ('\\', ?)");


Actual result:
--------------
Fatal error: Uncaught PDOException: SQLSTATE[42601]: Syntax error: 7 ERROR:  syntax error at or near ","
LINE 1: INSERT INTO test (col1, col2, col3) VALUES ('\', ?, ' ')
                                                          ^ in .../test2.php:11