jQuery Grid Plugin - jqGrid

I have this set as code in jqgrid, but changes are not being saved to database

$(function(){    $("#rota").jqGrid({    
url:'example.php',    
datatype: "json", 
mtype: 'POST',    
colNames:['Date', 'HPJ', 'Recycler','CCTV','Assistant'],    
colModel:[     
{name:'date',index:'date', width:90,editable:true},     
{name:'hpj',index:'hpj', width:100,editable:true},      
{name:'recycler',index:'recycler', width:100,editable:true},      
{name:'cctv',index:'cctv', width:100,editable:true},   
{name:'assistant',index:'assistant', width:100,editable:true}     ],
 rowNum:10,    
 rowList:[10,20,30],
 sortname: 'date',  
 viewrecords: true,   
 sortorder: "desc", 
 caption:"Weekend Call Out Rota", 
 pager : '#navGrid',   forceFit : true,
 cellEdit: true, cellsubmit :'remote',   
 cellurl : 'example.php'  });
 jQuery("#rota").jqGrid('navGrid','#navGrid',{edit:true,add:true,del:true});  });
 
I am also unable to add new rows: no url set