数据驱动的下拉菜单

I currently have an HTML form where the options for a certain drop-down menu are hard-coded. Instead, I want to use PHP to...

1. Look up the values in a column (cities) in a MySQL table (locations)
2. Make those values the only options in the dropdown menu.

Any ideas how I would do this? This is what I have so far.

<?php

 //connect to the database
 $dbc = mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);

 //grab the city names from the MySQL table 
 $query = "SELECT cities FROM locations";
 $data = mysqli_query($dbc, $query);

 //close the db connection
 mysqli_close($dbc);

?>

....Omitted a bunch of HTML here....

<label for="city">What is your destination city?</label>
      <select class="form-control" id="city" name ="city" /><br />
          <option value="$data">$data</option>
      </select>

<label for="city">What is your destination city?</label>
<select class="form-control" id="city" name="city">

<?php
  //connect to the database
  $dbc = mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);

  //grab the city names from the MySQL table 
  $query = "SELECT cities FROM locations";

  $res = mysqli_query($dbc, $query);

  while ($data = mysqli_fetch_assoc($res)) {
    echo '<option value="'.$data['cities'].'">'.$data['cities'].'</option>';
  }

  //close the db connection
  mysqli_close($dbc);
?>

</select>