Multivalue in combobox

[MFS]

Hello.
I have a combobox with some values.
I want to post as one sting, but I always recive two valus like this SRadnik=1&SRadnik=6 or other values but in this format.
I need it in format SRadnik='1,6'.
How to fix it?
This is my form:

Code:

									<div class="easyui-tabs" style="width:456px;height:85px">
										<div title="Podaci" style="padding:10px">
											<div class="fitem">
												<label>Serviser:</label>
												<input id="SRadnik" class="easyui-combobox" name="SRadnik" multiple="multiple" editable="false" multivalue="false" data-options="valueField:'Sifra',textField:'ImePrezime',url:'Pomocni/LookSRadnik.php'"  required="true" >
												<script>
													$('#SRadnik').combobox({
													  formatter:function(row){
														var opts = $(this).combobox('options');
														return '<input type="checkbox" class="combobox-checkbox">' + row[opts.textField]
													  },
													  onSelect:function(row){
														console.log(row)
														var opts = $(this).combobox('options');
														var el = opts.finder.getEl(this, row[opts.valueField]);
														el.find('input.combobox-checkbox')._propAttr('checked', true);
													  },
													  onUnselect:function(row){
														var opts = $(this).combobox('options');
														var el = opts.finder.getEl(this, row[opts.valueField]);
														el.find('input.combobox-checkbox')._propAttr('checked', false);
													  }
													})
												</script>
											</div>
										</div>
									</div>

[jarry]

Please look at this example http://code.reloado.com/ofomus4/edit#preview. It works fine.