[SERVER_PORT] when using proxy-server

[xendex]

I'm using Litespeed SE(as backend for scripts, on port 8080), nginx(as frontend proxy-server, on port 80) and PHP LSAPI, where each site(domain) has own vhost, php.ini, listener with own port(8081, 8082...)
And the problem is that some php-scripts(like phpBB3, phpMyAdmin) are using port(requesting it by _SERVER['SERVER_PORT']) in the redirection URL if it's not 80 by default - so URL redirects like http://mysite.com:8081/blah.php?=blah...... lead to an error.
So is there any way to return port 80(in _SERVER['SERVER_PORT']) dy default for all vhosts instead of port mentioned in the listener for this vhost(i.e. 8081, 8082, 8083...)? And does this have to be done on Litespeed, nginx or PHP level?
I will be glad to listen to any helpful solution.

Thanks in advance!

P.S. If it'll be useful, here's example nginx config, that I'm using for each vhost:

server { 
        listen       80; 
        server_name  mysite.com; 

        location / { 
proxy_pass         http://127.0.0.1:8081/; 
proxy_redirect     off; 
proxy_set_header   Host             $host; 
proxy_set_header   X-Real-IP        $remote_addr; 
proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for; 
client_max_body_size       10m; 
client_body_buffer_size    128k; 
proxy_connect_timeout      90; 
proxy_send_timeout         90; 
proxy_read_timeout         90; 
proxy_buffer_size          4k; 
proxy_buffers              4 32k; 
proxy_busy_buffers_size    64k; 
proxy_temp_file_write_size 64k; 
        } 

 # Static files location 

        location ~* ^.+.(jpg|jpeg|gif|png|css|zip|tgz|gz|rar|bz2|doc|xls|exe|pdf|ppt|txt|tar|wav|bmp|rtf|js)$ { 

                    root   /home/somesites/domains/mysite.com/public_html/; 

                            } 



        error_page   500 502 503 504  /50x.html; 
        location = /50x.html { 
            root   html; 
        } 

        location ~ /.ht { 
            deny  all; 
        } 
    }