Description:
------------
Since 5.4.4 there's  an `escape_char` parameter that's defaulting to \. 

It looks like that parameter is meaningless though as of all the possible values passed in, only " really does something and what it does is break the CSV encoding.

Test script:
---------------
<?php

$fh = fopen('php://stdout', 'w');
fputcsv($fh, ['using default', 'a,"b'], ',', '"');
fputcsv($fh, ['using "      ', 'a,"b'], ',', '"', '"');
fputcsv($fh, ['using x      ', 'a,"b'], ',', '"', 'x');
fputcsv($fh, ['using \\      ', 'a,"b'], ',', '"', '\\');

Expected result:
----------------
"using default","a,\"b"
"using "      ","a,""b"
"using x      ","a,x"b"
"using \      ","a,\"b"

Actual result:
--------------
"using default","a,""b"
"using "      ","a,"b"
"using x      ","a,""b"
"using \      ","a,""b"