xxxxxxxxxx
// output up to 5MB is kept in memory, if it becomes bigger it will
// automatically be written to a temporary file
$csv = fopen('php://temp/maxmemory:'. (5*1024*1024), 'r+');
fputcsv($csv, array('blah','blah'));
rewind($csv);
$output = stream_get_contents($csv);
// Put the content directly in file into the disk
Storage::disk('myDisk')->put("report.csv", $output);