Description:
------------
There is a problem with single backlash string in parametrized qurery. When I try run test script it gives me error. String with backslash is quoted with PDO::quote with posgresql driver. It seems valid if not used with parametrized query with next string with quotes.
Valid sql:
INSERT INTO test_quote ("id","text","text2","text3","text4") VALUES (1,'aaa',?,'\','test4')
Invalid sql:
INSERT INTO test_quote ("id","text","text2","text3","text4") VALUES (1,'aaa','\',?,'test4')
It affects all versions of php from 5.5 and above what I tested.


Test script:
---------------
$dbh = new PDO('pgsql:host=postgres;dbname=test','test_user','test');
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$dbh->exec('DROP TABLE IF EXISTS test_quote');
$dbh->exec('CREATE TABLE test_quote ( id int, text varchar(40), text2 varchar(40), text3 varchar(40), text4 varchar(40) )');

$sql = <<<'EOT'
INSERT INTO test_quote ("id","text","text2","text3","text4") VALUES (1,?,'\',?,'test4')
EOT;
try {
  $statement = $dbh->prepare($sql);
  $statement->bindValue( 1 , 'test1', PDO::PARAM_STR);
  $statement->bindValue( 2 , 'test3', PDO::PARAM_STR);
  $statement->setFetchMode(PDO::FETCH_ASSOC);
  $statement->execute();
} catch (PDOException $e) {
  echo 'Connection failed: ' . $e->getMessage();
}


Actual result:
--------------
Connection failed: SQLSTATE[42601]: Syntax error: 7 ERROR:  syntax error at or near ","
LINE 1: ...,"text","text2","text3","text4") VALUES (1,$1,'\',?,'test4')
                                                              ^