To overcome the 2GB file size limit, you can open your own socket to get the file size of a large file. Quick and dirty script:
<?php
$socket=fsockopen($hostName, 21);
$t=fgets($socket, 128);
fwrite($socket, "USER $myLogin\r\n");
$t=fgets($socket, 128);
fwrite($socket, "PASS $myPass\r\n");
$t=fgets($socket, 128);
fwrite($socket, "SIZE $fileName\r\n");
$t=fgets($socket, 128);
$fileSize=floatval(str_replace("213 ","",$t));
echo $fileSize;
fwrite($socket, "QUIT\r\n");
fclose($socket);
?>