$maxFiles public property
The maximum file count the given attribute can hold. Defaults to 1, meaning single file upload. By defining a higher number, multiple uploads become possible. Setting it to 0 means there is no limit on the number of files that can be uploaded simultaneously.
Note: The maximum number of files allowed to be uploaded simultaneously is also limited with PHP directive max_file_uploads, which defaults to 20. See also:
http://php.net/manual/en/ini.core.php#ini.max-file-