<?
$data = array('a\\', '\\b', 'c');
$f = fopen('php://memory', 'w+');
fputcsv($f, $data);
fseek($f, 0, 0);
$mangled = fgetcsv($f);
fclose($f);

print_r($data);
print_r($mangled);

Array
(
    [0] => a\
    [1] => \b
    [2] => c
)
Array
(
    [0] => a\",\b"
    [1] => c
)