Combobox master detail problem

[MFS]

Hello.
I have two comobox in master detail relations.
In detail combobox I cant made it multiselect.
Why?

Code:

<div class="fitem">
	<label>Tabela:</label>
	<input id="Tabela" class="easyui-combobox" name="Tabela" 
	data-options="
			valueField:'Sifra',
			textField:'Naziv',
			url: 'LookTabela.php',
			onSelect: function(rec)
			{
				var url = 'LookPolja.php?TabelaID='+rec.Sifra;
				$('#Polja').combobox('reload', url);
			}
				" required="true" >
</div>
<div class="fitem">
	<label>Polja:</label>
	<input id="Polja" class="easyui-combobox" name="Polja" 
	data-options="
			valueField:'Sifra',
			textField:'Naziv', multiple:true " required="true" >
</div>

Why?
Also in detail I can only chose first one in combobox?

Code:

https://ibb.co/kMhOHQ

[stworthy]

No problem. You have set 'multiple' to true, you can select multiple items in your combobox component. Please look at this example https://www.jeasyui.com/demo/main/index.php?plugin=ComboBox&theme=material&dir=ltr&pitem=Multiple%20Select&sort=

[MFS]

I made that allready.
Look at my code.

[stworthy]

Please look at this example http://code.reloado.com/obosob4/edit#javascript,html