It depends on the underlying API used for the network operations, the php's stream 
implementation.

PHP's stream does not support yet LFS and cannot support it easily by only using 
long instead of int (while this breaks the api signature too).

Suspended until we have lfs support.

Stumbled across this issue just thought I would toss in my solution. Just queries 
the ftp server for the size and converts the resulting string to a double rather 
than an int.

$size = 0;
$result = ftp_raw($conn_id, "SIZE " . <file path>);
$parts = explode(" ", $result[0]);
if($parts[0] === "213") {
    $size = doubleval($parts[1]);
}

The suggested patch uses long instead. 

Double is not a good value for file sizes as discussed here: https://bugs.php.net/bug.php?id=44522  https://github.com/php/php-src/pull/372

This is fixed for 64bit POSIX systems as of PHP 5.4.20[1], and is
unlikely to get fixed for 32bit systems.  However, it won't work
for 64bit Windows, since the function uses atol()[2] which returns
a long.

[1] <http://git.php.net/?p=php-src.git;a=commit;h=a93a462>
[2] <https://github.com/php/php-src/blob/php-7.2.8/ext/ftp/ftp.c#L1144>