PHP mysql查询返回一个空白屏幕

Question

I've commented out the bottom part, and the SQL query works fine. Its the displaying of the query where the error is coming from i believe.

$host = "127.0.0.1"; 
$user = "root"; 
$pass = "Toom13371!";

$connection = mysql_connect($host,$user,$pass) or die (mysql_errno().":     ".mysql_error()."<BR>");

// 2. Selecting DB.

$dbname = "filters"; 
mysql_select_db($dbname);

// 3. Build/Test SQL Query

$sql = ("select * from filter_bandpass where start_passband=" . $_POST['Lowfreq'] . "         and stop_passband='" . $_POST['Highfreq'] . "'");
//echo $sql; //Comment/Uncomment to test sql query.

// 4. Retrieve info from MySQL.

$query = mysql_query($sql);

// 5. Display Query.

echo "<table border='1'>
<tr>
<th>Low Frequency</th>
<th>High Frequency</th>
</tr>";

while($row = mysql_fetch_array($query)) {
  echo "<tr>";
  echo "<td>" . $row['Lowfreq'] . "</td>";
  echo "<td>" . $row['Highfreq'] . "</td>";
  echo "</tr>";
}

echo "</table>";
  ?>

Any help would be appreciated, I'm sure it's going to be some small stupid error i've over looked.

Thanks in advance :)

Answer 1

I'm guessing, based on your query, that you need to change this

mysql_select_db($dbname);

to

mysql_select_db($dbname, $connection);

and

while($row = mysql_fetch_array($query)) {
  echo "<tr>";
  echo "<td>" . $row['Lowfreq'] . "</td>";
  echo "<td>" . $row['Highfreq'] . "</td>";
  echo "</tr>";
}

to

while($row = mysql_fetch_array($query)) {
  echo "<tr>";
  echo "<td>" . $row['start_passband'] . "</td>";
  echo "<td>" . $row['stop_passband'] . "</td>";
  echo "</tr>";
}