How to pass data from database to combobox?

Question

I wanted to put some data from the database in a combobox but I’m not getting it, I think the problem will be the connection to the database but I don’t know what will be wrong, can help me?

<?php
...
$dbconn = mysqli_connect($servername, $username, $password, $dbname)or die("Failed to connect to database:" . mysqli_error($dbconn));

$query = "SELECT nome FROM Medicos";
$data = mysqli_query($dbconn, $query);
$result = mysqli_num_rows($data);       

?>
  <form name="medicos" method="post" action="">
  <label for="">Selecione um m&eacute;dico</label>
  <select>
  <option>Selecione...</option>

<?php while($prod = $result->fetch_assoc()) { 
   echo '<option value="'.$prod['nome'].'">'.$prod['nome'].'</option>';
   }
?>    
</select>

Answer 1

Do your while on variable $data because it is she who made the Query execution

<?php

...
$dbconn = mysqli_connect($servername, $username, $password, $dbname)or die("Failed to connect to database:" . mysqli_error($dbconn));

$query = "SELECT nome FROM Medicos";
$data = mysqli_query($dbconn, $query);
$result = mysqli_num_rows($data);       

?>
  <form name="medicos" method="post" action="">
  <label for="">Selecione um m&eacute;dico</label>
  <select>
  <option>Selecione...</option>

<?php while($prod = $data->fetch_assoc()) { 
   echo '<option value="'.$prod['nome'].'">'.$prod['nome'].'</option>';
   }
?>    
</select>