To overcome the 2 GB limitation, the ftp_raw solution below is probably the nicest. You can also perform this command using regular FTP commands:

<?php
$response =  ftp_raw($ftpConnection, "SIZE $filename");
$filesize = floatval(str_replace('213 ', '', $response[0]));
?>

[However, this] is insufficient for use on directories. As per RFC 3659 (http://tools.ietf.org/html/rfc3659#section-4.2), servers should return error 550 (File not found) if the command is issued on something else than a file, or if some other error occurred. For example, Filezilla indeed returns this string when using the ftp_raw command on a directory:

array(1) {
  [0]=>
  string(18) "550 File not found"
}

RFC 959 (http://tools.ietf.org/html/rfc959) dictates that the returned string always consists of exactly 3 digits, followed by 1 space, followed by some text. (Multi-line text is allowed, but I am ignoring that.) So it is probably better to split the string with substr, or even a regular expression.

<?php
$response = ftp_raw($ftp, "SIZE $filename");
$responseCode = substr($response[0], 0, 3);
$responseMessage = substr($response[0], 4);
?>

Or with a regular expression:

<?php
$response = ftp_raw($ftp, "SIZE $filename");
if (preg_match("/^(\\d{3}) (.*)$/", $response[0], $matches) == 0)
    throw new Exception("Unable to parse FTP reply: ".$response[0]);
list($response, $responseCode, $responseMessage) = $matches;
?>

You could then decide to assume that response code '550' means that it's a directory. I guess that's just as 'dangerous' as assuming that ftp_size -1 means that it's a directory.

Just to let people out there know, on my windows 2000 server running Apache and php i was returned 0 not -1 for directories.

foreach ($dir_list as $item)
    {
      if(ftp_size($conn_id, $item) == "0")
      {
      echo "<br>Directory:: ".$item;
      } else {
      echo "<br>File:: ".$item;
      }
    }

This outputs a list of the remote directory and indicates which items are directories and which are files.

If you experience troubles with size of large file then you can use ftp_rawlist function and parse it result

note that project_t4 at hotmail dot com's example above doesn't work in general, though it works on his Win2K/Apache server; as far as I can tell there is no way to check over ftp whether a directory exists.  This function's behavior given a directory name seems to be at least somewhat dependent on your OS, web server, or ftp server, I don't know which.

Well this function is nice but if you have files larger then 2.1Gb or 2.1 Billion Bytes you cannot get its size.

To get a dirsize recursive you can use this simple function:

<?php # copyright by fackelkind | codeMaster
    function getRecDirSize ($connection, $dir){
        $temp = ftp_rawlist ($connection, "-alR $dir");
        foreach ($temp as $file){
            if (ereg ("([-d][rwxst-]+).* ([0-9]) ([a-zA-Z0-9]+).* ([a-zA-Z0-9]+).* ([0-9]*) ([a-zA-Z]+[0-9: ]*[0-9]) ([0-9]{2}:[0-9]{2}) (.+)", $file, $regs)){  
                $isdir = (substr ($regs[1],0,1) == "d");
                if (!$isdir)
                    $size += $regs[5];
            }
        }
        return $size;
    }
    $dirSize = getRecDirSize ($conID, "/");
?>

This will return the filesize on remote host and the size if you download it in FTP_BINARY mode. If you are using FTP_ASCII in ftp_get() the size can be changed.

$file= 'filename with space.txt';
$size = ftp_size($this->ftp, urldecode($file) );

this one can correctly return the size
otherwize, it always return -1

2 adams[AT]techweavers[DOT]net:
To get a size of large file (f. ex.: 3.2 Gb) you have to format the result returned by ftp_size():

$size = sprintf ("%u", ftp_size($connection, $file_name));

So you can get the real size of big files. But this method is not good for checking is this a dir (when ftp_size() returns -1).

For checking if a certain folder exists try using ftp_nlist() function to get a directory list in array. By using in_array('foldername') you can find out if it is there or not.

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);
?>