<?php 
include('conn.php');
$state_id = $_POST["state_id"];
$city = $con ->query("SELECT * FROM cities Where state_id='$state_id'");                                                       
?>
<option value="">Select City</option>
<?php
while($city_data = $city ->fetch_assoc()){
?>
<option value="<?php echo $city_data["city_id"];?>"><?php echo $city_data["city_name"];?></option>
<?php
}
?>