The PHP ftp_alloc() function allocates space for a file to be uploaded to the FTP server.

<?php
// connect and login to FTP server
$ftp_server = 'ftp.example.com';

$ftp_conn = ftp_connect($ftp_server) or die('Could not connect to ' . $ftp_server);
$login = ftp_login($ftp_conn, $ftp_username, $ftp_userpass);

$file = '/test/my-file';

// allocate server space
if (ftp_alloc($ftp_conn, filesize($file), $result)) {
    echo 'Space allocated on server';
    ftp_put($ftp_conn, '/files/my-file', $file, FTP_BINARY);
}
else {
    echo 'Error! Server said:' . $result;
}

// close connection
ftp_close($ftp_conn);
?>

// allocates space for a file and uploads the file to the FTP server

ftp_alloc(ftp_conn, filesize, result)