在选择第二个选择框的类别时获取选择框的值

I need select box to load values on page load.

I have two select boxes if i select one option from first select box. than other select box loads the values from database but i need the other one select box value on page load which first select box select the category the second depend on that select box.

only the first selection of first select box should load the second select box value on page load not on my function of onChange().

<select name="delclassselected" id="delclassselected" onChange="selectSubject()" >
<?php echo($showclasssvalue); ?>
</select>