How do you add parameters to an Ajax store?

I am bypassing the cross domain policy by using a php proxy on my server. I am trying to send a few needed parameters to the php page and I expect the response to be xml.

But how do I send certain parameters to the php page on the server?

PHP Code:
  var orderStore = new Ext.data.Store({
            
model'order',
            
urlvarxml,
            
proxy: {
                
type:'ajax',
                
id'data',
                
url'proxytest.php',
                
method"POST",
                
params:{action'askorderlist',
                     
question'uborderlist',
                     
value'2010-08-01',
                     
user'username',
                     
password'password'
                 
},
                
reader: {
                    
type'xml',
                    
record'order'
                
}
            },
    
autoloadtrue,
    });