Modifying contents of text file and filenames with random data

[L0Y4L1S3R]

I have multiple (about 40) text files on a web server that contain the following line of text (each file contains the exact information, except for the "randomize" part which contains random text for each file):

rtsp://rrr.domainname.com/2376/randomize.rm

Examples:
rtsp://rrr.domainname.com/2376/34mngh4732.rm -> video1.ram
rtsp://rrr.domainname.com/2376/po94hnw462.rm -> video2.ram
rtsp://rrr.domainname.com/2376/qwun47hvc8.rm -> video3.ram

I need a script that will open each one of these files, replace the "randomize" text with a new random alphanumeric value that is 10-digits long.

After this occurs, I need the script to login to an FTP server and rename the actual randomize.rm file to the new 10-digit random value.

The purpose of this question is to prevent users from saving the .ram files to their computer and being able to access the .rm videos any time. I want to force them to login first via the PHP login page.

Thank you!

[Installer]

This is untested and has no error-checking, but it should come close:

$local_dir = 'local/dir';
$remote_server = 'example.com';
$remote_dir = 'remote/dir';
$char_arr = array_merge(range('a', 'z'), range('0', '9'));
$name_len = 10;

$dh = dir($local_dir);
while (($file = $dh->read()) !== false) {
    if (substr($file, -4) == '.ram') {
        $rand_str = '';
        for ($i = 0; $i < $name_len; $i++) {
            $rand_str .= $char_arr[mt_rand(0, count($char_arr) - 1];
        }
        $contents = trim(file_get_contents($file));
        $old_name = ltrim(strrchr($contents, '/'), '/');
        $new_names[$old_name] = $rand_str;
        $new_contents = str_replace($old_name, $rand_str . 'rm', $contents);
        $fp = fopen($file, 'wb');
        fwrite($fp, $new_contents);
        fclose($fp);
    }
}
$dh->close();

$connection = ftp_connect($remote_server); 
$login = ftp_login($connection, $user, $pword); 
$remote_files = ftp_nlist($connection, $remote_dir);
foreach ($remote_files as $file) {
    if (array_key_exists($file, $new_names)) {
        ftp_rename($connection, $file, $new_names[$file] . 'rm');
    }
}
ftp_close($connection);