Use rsync to upload files from local to remote server from inside php script without typing password

I have already set up a public key to automate the login on remote server for my user.

So this is running without any problem from cli:

rsync -r -a -v -e "ssh -l user" --delete ~/local/file 111.111.11.111:~/remote/;

But, when I try to run the same from a PHP script (on a webpage in my local server):

$c='rsync -r -a -v -e --log-file=FILE "ssh -l user" --delete ~/local/file 111.111.11.111:~/remote/';

//exec($c,$data);
passthru($c,$data);
print_r($data);

This is what I receive:

2011/01/23 19:18:29 [6401] rsync: connection unexpectedly closed (0 bytes received so far) [sender] 2011/01/23 19:18:29 [6401] 
rsync error: unexplained error (code 255) at io.c(601) [sender=3.0.7] 

The permissions qre set like this:

Local:
chmod 600 ~/.ssh/local-rsync-key
chmod 600 ~/.ssh/local-apache-key
chmod 700 ~/.ssh/

Remote:
chmod 600 ~/.ssh/authorized_keys
chmod 700 ~/.ssh/
chmod 700 ~/

I registered two keys on ~/.ssh/authorized_keys:

user@localserver
apache@localserver

I went dry of ideas... I guess I have to do something else in the remote /etc/ssh/sshd_config file. I am running Nginx in both servers. Thanks for any help.

UPDATE:

While I cannot get rsync, this is how I got to transfer the file from local to remote:

if($con=ssh2_connect('111.111.11.111',22)) echo 'ok!';
if(ssh2_auth_password($con,'apache','xxxxxx')) echo ' ok!';
if(ssh2_scp_send($con,'localfile','/remotefolder',0755)) echo ' ok!';

Local file needs: 0644 Remote folder needs: 0775

I also read this suggestion: "I don't think you want to "copy the key somewhere where apache can get to it" - that's a security violation. Better to change the script to run as a secure user and then setup the .ssh keys for passwordless login between servers.

If somebody know how to do this, please, it would be of great help.