<?php
$con = mysqli_connect("localhost","root","","db_name");
$select_material_code = "SELECT emp_id, emp_name FROM employees";
$get_material_code = mysqli_query ($con, $select_material_code);
$options_material_Code = "<option>--Select Product--</option>";
$option_material_description = "";
while ($result_material_code = mysqli_fetch_array($get_material_code))
{
$options_material_Code.= "<option value=".$result_material_code[1].">$result_material_code[1]</option>";
}
?>
<script type="text/javascript" src="//code.jquery.com/jquery-1.8.0.min.js"></script>
<select name="materialcode_1" id="materialcode_1">
<?php echo $options_material_Code; ?>
</select>
<input type="text" name="description_1" placeholder="Description" maxlength="40" size="40" value="" id="description_1">
<script>
$("#materialcode_1").change(function(e) {
$("#description_1").val($("#materialcode_1").val())

});
</script>