Description:
------------
SplFileObject::__toString() is an alias of ::current(), but since
the latter returns an array instead of a string, if the READ_CSV
flag is set, the former also does.  This is at least rather
confusing, since one expects __toString() to return a string.

See also <http://php.net/manual/en/splfileobject.tostring.php#123238>.

Test script:
---------------
<?php
$file = new SplTempFileObject;
$file->fputcsv(['foo', 'bar', 'baz']);
$file->rewind();
$file->setFlags(SplFileObject::READ_CSV);
echo gettype($file->__toString());
?>

Expected result:
----------------
string

Actual result:
--------------
array