Description
The amount of bytes specified as buffer size is the maximum amount
of data read at once from resources or files.
The default size is 2M (2097152 bytes).
Be aware that if you enable gzip compression and
you set a very low buffer size that the actual file size may grow
due to added gzip headers for each sent chunk of the specified size.
Returns PEAR_Error
(HTTP_DOWNLOAD_E_INVALID_PARAM)
if $size is not greater than 0 bytes.
