PHP No Headers

<?php
$sql = $_POST['query'];
if ($sql == ''){
echo "Empty search!";
}
else{
$result = mysqli_query($conn, $sql);
if (($result)||(mysql_errno == 0))
{
  echo "<table width='50%'><tr>";
  if (mysqli_num_rows($result)>0)
  {
          //loop thru the field names to print the correct headers
          //$i = 0;
          //while ($i < mysqli_num_fields($result))
          //{
       //echo "<th>". mysqli_fetch_fields($result) . "</th>";
       //$i++;
    //}
    //echo "</tr>";

    //display the data
    while ($rows = mysqli_fetch_assoc($result))
    {
      echo "<tr>";
      foreach ($rows as $data)
      {
        echo "<td align='center'>". $data . "</td>";
      }
    }
  }else{
    echo "<tr><td colspan='" . ($i+1) . "'>You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax.</td></tr>";
  }
  echo "</table>";
}
else{
  echo "Error in running query :". mysqli_error();
}
}
?>