I have class project which I have to submit monday on student department selection system in php.I face difficulty on some part.I want to get student's department selection in order and store it in database.For example : when the student select medicine selection ,I want the selected option hidden from the second selection options using php and mysql and also javascript.Help me please code snippet..

<label>select your first choice</label>
<select class="custom-select" name="choice_1" required>
    <option value="">Choose ...</option>
    <option value="Engineering">Engineering</option>
    <option value="Medicine">Medicine</option>
    <option value="Pharmacy">Pharmacy</option>
</select>

<label>select your second choice</label>
 <select class="custom-select" name="choice_2" required>
     <option value="">Choose...</option>
     <option value="Engineering">Engineering</option>
     <option value="Medicine">Medicine</option>
     <option value="Pharmacy">Pharmacy</option>
</select>
 <label>select your third choice</label>
 <select class="custom-select" name="choice_3" required>
      <option value="">Choose...</option>
      <option value="Engineering">Engineering</option>
      <option value="Medicine">Medicine</option>
      <option value="Pharmacy">Pharmacy</option>