ExtJS Ajax request passing json parameter

var myObj = {
 param1 : 'something',
 obj1    : {
    a : 'something in obj1'
 }

}
Ext.Ajax.request({
	   	url: session_manager_url,
	   	method: 'POST',
	      	params: {
	   				ajax_req: Ext.util.JSON.encode(myObj)
			},
	   	success: function(transport){
                  // do something
	   	},
	   	failure: function(transport){
	   			alert("Error: " - transport.responseText);
	   	}
	});

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