Persist an FTP connection PHP resource across AJAX calls

Question

I have a multi-user PHP web application that can interact with an FTP server via AJAX. The application allows the user to browse an FTP site. Javascript makes an AJAX call which communicates with a server-script that returns a list of files and directories within a given directory.

This works fine. However, each time a directory listing is requested, the server must re-establish a connection with the FTP server, which takes a lot of time.

I need to persist an FTP connection PHP resource across AJAX calls. In other words, the connection must remain open, and I must be able to run ftp_nlist() using that resource, without re-establishing the connection or re-authenticating, with each new AJAX call (until the connection times out, of course).

Can anyone think of a way to do this?

Answer 1

I ended up making this work using global variables (eg. $my_global). I have a ConnectionPooler singleton class which manages connections stored in a hash.

Answer 2

I don't think it's possible using the FTP library in PHP. I see somebody even had a feature request for it in PHP, but it doesnt seem there was any action taken on it.

The only way I can think of is to use a 3rd-party FTP client that keeps the connection open and interface with it through PHP. (instead of a 3rd party ftp client, you could just use the FTP functions built-in to the OS. Windows provides them, as does Linux through the "ftp" program.)

Answer 3

Sorry to add clutter without a clear answer for ya but this might be helpful: http://www.eecho.info/Echo/php/client-url-library-php-curl/ It appears you are in control of opening and closing the connections however in terms of returning this variable to the client and having it re-used I'm not sure that is possible (also it might just clean itself up out of your control), alternatively you might (depending on the end environment) consider using a Java backend, you could code up a simple server and just add the FTP code on top (mmm... cake). Some examples of what you'd need to do for that are here:

http://fragments.turtlemeat.com/javawebserver.php

http://www.javaworld.com/javaworld/jw-04-2003/jw-0404-ftp.html

This assumes a pretty large amount of control of what's run in the server environment though so really depends on you owning the server basically or having full priveleges to do do what you want (like Amazon EC2 from what they advertise at least). You might be able to pull this off with Tomcat or some other JSP container and use JSPs instead of writing your own server but I don't know that you'd be able to persist the connection their either since it's sort of the same as PHP where the server generally interprets the file "on the fly" so to speak.

Answer 4

You can not create a persistent FTP connection with PHPs normal ftp classes functions. Are all users accesing the same ftp server or are you running a ftp web interface? If multiple users are connected to the same server (with the same rights) you could implement a cached solution.