Description:
------------
Regarding the field enclosure parameter in fputcsv...

1. It's unrealistic to require the field enclosure to be one character because it's very common to have "empty string" as the field delimiter (especially when TAB is used as field delimiter).  I tried to use "\0" as the field enclosure, hoping that'd be interpreted as an empty string, but fputcsv translated it into literal.

2. fputcsv wrongly adds the field enclosures whenever a field contains a space. The expected behavior should be adding the field enclosures when a field contains a field delimiter.


Reproduce code:
---------------
/*
test_in.csv has only one line:
$line = "field 0\tfield_1\tfield 2\n";
*/

$fh_in=fopen("test_in.csv","r");
$fh_out=fopen("test_out.csv","w");

// since "" is not accepted as the 4th parameter, I use "\0" instead
$fields = fgetcsv($fh_in, 0, "\t", "\0");
fputcsv($fh_out, $fields, "\t", "\0");

close($fh_in);
close($fh_out);

Expected result:
----------------
/*
One would expect to see in test_out.csv :
$line = "field 0\tfield_1\tfield_2\n";
*/

Actual result:
--------------
/*
However, the result shows:
$line = "\0field 0\0\tfield_1\t\0field 2\0\n";

Unexpected:
1. Since space is not the field delimiter, there is no point of using the field enclosure.

2. Empty enclosure is very common and should be accepted.
*/