How to get option value using php?

<form method = "post">
    <div class="form-group">
          <label for="companyType">Company type</label>
          <select class="form-control" id="companyType" name="companyType">
              <option value="1">clothes</option>
               <option value="2">art</option>
               <option value="3">furniture</option>
               <option value="4">real state</option>
               <option value="5">car</option>
               <option value="6">electronics</option>
               <option value="7">book</option>
               <option value="8">toy</option>
               <option value="9">building materials</option>
          </select>
    </div>              
    <button type="submit" name="companyRegister" class="btn btn-default">Register </button>
</form>

if(isset($_POST['companyRegister'])){
    echo data['companyType'];
}