The maxGetUrlLength property of the layer's
            tileOptions option causes tiles to be requested using
            HTTP POST when the length of the GET url would exceed the specified
            length (2048 characters is recommended). In real life applications,
            this happens often when using the SLD_BODY request parameter for
            inline styling.
        
            
            Long URL - POST requests
            
            
            Short URL - GET requests
        
View the wms-long-url.js source to see how this is done.