javascript change option and populate a input box a php variable


How do I populate an input box a php variable when I change an option in a dropdown box?
I am using cakephp and I need to add the textbox assignment in the 2 date fileds using  js as below
function myFunc(val) {
    if(val != 4) {
        document.getElementById("startdatebox").disabled = true;
        document.getElementById("enddatebox").disabled = true;
    } else {
        document.getElementById("startdatebox").disabled = false;
        document.getElementById("enddatebox").disabled = false;

   echo $this->Form->input('dateRange', array('label' => 'Date Range','id'=>'dateRange',
                      'options' => $dateRange,'style'=>'width:150px','selected' => $dateSelect ,'onclick'=> 'myFunc(this.value)' ));
         echo $this->Form->input('startDate',array('id'=>'startdatebox','label' => 'Start Date','class'=>'datepicker', 
                    'type'=>'text','style'=>'width:100px;height:30px','value' => $datestart,'readonly' => 'readonly'));
            echo '</td>';
            echo '<td>';
            echo $this->Form->input('endDate',array('id'=>'enddatebox','label' => 'End Date','class'=>'datepicker', 
                     'type'=>'text','style'=>'width:100px;height:30px','value' => $dateend,'readonly' => 'readonly'));


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Chris StanyonWebDevCommented:
You seem to be mixing up your client-side code (javascript) with your server-side code (php), so it's not really clear what you need.

Can you please clarify exactly what you mean.
jagguyAuthor Commented:
I want to assign a textbox a date value when I change an option box. This value to assign is stored in php variable so how do I do this?
Chris StanyonWebDevCommented:
Javascript does not have access to PHP - one is server-side and one is client-side.

Tell us what you mean by an option box - there's no such thing in HTML.

Do you want to update a textbox when you change a select dropdown?

Still struggling to understand what you need
jagguyAuthor Commented:
Do you want to update a textbox when you change a select dropdown?

Chris StanyonWebDevCommented:
OK. Here's a very basic way to do it:


<select id="mySelect">
    <option value="">Please Select...</option>
    <option value="option1">Option 1</option>
    <option value="option2">Option 2</option>
    <option value="option3">Option 3</option>
    <option value="option4">Option 4</option>

<input type="text" id="myText" />

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The jQuery:

$('#mySelect').change(function() {
    $('#myText').val( $(this).val() );

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The Working Demo:

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