如何从动态生成的html-table中删除选定的列？

Question

我有一个SQL数据库，我在其中读出数据，然后在动态生成的html表中显示这些数据。下面是我的代码，运行得很好：

$sql = "SELECT $selection FROM $tabelle WHERE $masterarray";


$result = mysqli_query($db, $sql) or die("Invalid query");             
$numrows = mysqli_num_rows($result);  
$numcols = mysqli_num_fields($result); 
$field = mysqli_fetch_fields($result); 


if ($numrows > 0) {

echo "<table>";
echo "<thead>";
echo "<tr>";
echo "<th>" . 'Nr' . "</th>";


for($x=0;$x<$numcols;$x++){
echo "<th>" . $field[$x]->name . "</th>";
}

echo "</tr>";
echo "</thead>";

echo "<tbody>";
echo "<tr>";
$nr = 1;

while ($row = mysqli_fetch_array($result)) {
  echo "<td>" . $nr . "</td>";
  for ($k=0; $k<$numcols; $k++) {    
  echo "<td>" . $row[$k] . "</td>"; //Prints the data
  }

 $nr = $nr + 1;
 echo "</tr>";

 }
 echo "</tbody>";
 echo "</table>";

}
}

mysqli_close($db); 

现在，我想删除特定的列(例如，那些为空的列，或者那些对发出请求的用户不是很感兴趣的列)。

我在unset($field[$variable])上试过了，但是它不起作用。此外，还应该删除这些值(如果有)。

Answer 1

始终在打印数组之前对其进行格式化。在回显$field之前，尝试从HTML数组中删除特定的列，然后打印最终的表。一旦HTML代码在PHP中得到回显，如果不使用JavaScript，就无法将其删除。

您可以对照$field[$x]->name变量进行检查，并使用continue跳过该列。

Answer 2

可以让mysql为你过滤掉它们，$sql = "SELECT $selection FROM $tabelle WHERE $masterarray AND LENGTH($selection) > 0";

-- http://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_length

Answer 3

<?php

//  DataBase Config - http://php.net/manual/pt_BR/pdo.construct.php.
$dsn = 'mysql:host=localhost;dbname=test';
$usr = 'root';
$pwd = '';

try {   //  try to connect in database.

    $pdo = new PDO($dsn, $usr, $pwd);

} catch (PDOException $e) { //  if there is error in the connection.

    die('Connection failed: ' . $e->getMessage());

}

//  Prepare Statement and execute - http://php.net/manual/pt_BR/pdo.prepare.php.
$stm = $pdo->prepare('select id, weight, color, name from product');
$stm->execute();

//  Get ALL rows - Object.
$rows = $stm->fetchAll(PDO::FETCH_OBJ);

//  Print Rows.
//echo '<pre>'.print_r(rows, true).'</pre>';

//  Check $row;
if (count($rows)) {

    //  Order and Display Cols.
    $colsDisplay = [
        'id'        => 'ID Product',
        'name'      => 'Name',
        'weight'    => 'Weigth'
    ];

    //  Table.
    $html = '<table border="1">';
    $html .= "\n    <thead>";
    $html .= "\n        <tr>";
    $html .= "\n            <th  bgcolor='#eee'>Row</th>";
    $html .= "\n            <th>". implode("</th>\n         <th>", $colsDisplay) ."</th>";
    $html .= "\n        </tr>";
    $html .= "\n    </thead>";
    $html .= "\n    <tbody>";

    //  Loop ROWS.
    foreach ($rows as $key => $val) {

        $html .= "\n        <tr>";

        $html .= "\n            <td bgcolor='#eee'>". $key ."</td>";

        //  Loop COLS to display.
        foreach ($colsDisplay as $thKey => $thVal) {

            $html .= "\n            <td>". $val->$thKey ."</td>";

        }

        $html .= "\n        </tr>";

    }

    $html .= "\n".' </tbody>';
    $html .= "\n".'</table>';

    echo $html;

}