Yii - How To Change Ejuicombobox Option Value In Html

I’m new to Yii and I’m using the below code to create a dropdownlist.

<?php 

                    $this->widget('ext.combobox.EJuiComboBox', array(

                        'model' => $model,

                        'attribute' => 'max_cost',

                        // data to populate the select. Must be an array.

                        'data' => Yii::app()->params['cost_max_rental'],

                        // options passed to plugin

                        'options' => array(

                            'allowText' => false,

                        ),

                        // Options passed to the text input

                        'htmlOptions' => array('placeholder' => 'Max Cost', 'style'=>'width:70px'),

                    ));

                    

                    //echo $form->dropDownList($model,'city', Yii::app()->params['city'], array('style'=>'width:120px')); 

                    ?>

Now, the HTML generated is

    <select id="SearchForm_max_cost_select" style="display: none;">

    <option value="0"></option>

    <option value="300000.0">300000.0</option>

    <option value="400000.0">400000.0</option>

    <option value="500000.0">500000.0</option>

    <option value="600000.0">600000.0</option>

    </select>  

Now, why is the option value not mentioned as 0, 1, 2, 3. How can I change it

    <select id="SearchForm_max_cost_select" style="display: none;">

        <option value="0"></option>

        <option value="1">300000.0</option>

        <option value="2">400000.0</option>

        <option value="3">500000.0</option>

        <option value="4">600000.0</option>

        </select>