Delete multiple rows by selecting checkboxes using PHP

I want to delete multiple rows from MYSQL database. I have created this delete.php file to select various links and delete them using checkboxes.

<html>
<head>

<title>Links Page</title>

</head>

<body>

<h2>Choose and delete selected links.</h2>

<?php

$dbc = mysqli_connect('localhost','root','admin','sample')
or die('Error connecting to MySQL server');

$query = "select * from links ORDER BY link_id";

$result = mysqli_query($dbc,$query)
or die('Error querying database');

$count=mysqli_num_rows($result);
?>

<table width="400" border="0" cellspacing="1" cellpadding="0">
<tr>
<td><form name="form1" method="post" action="">
<table width="400" border="0" cellpadding="3" cellspacing="1" bgcolor="#CCCCCC">
<tr>
<td bgcolor="#FFFFFF">&nbsp;</td>
<td colspan="3" bgcolor="#FFFFFF"><strong>Delete multiple links</strong> </td>
</tr>
<tr>
<td align="center" bgcolor="#FFFFFF">#</td>
<td align="center" bgcolor="#FFFFFF"><strong>Link ID</strong></td>
<td align="center" bgcolor="#FFFFFF"><strong>Link Name</strong></td>
<td align="center" bgcolor="#FFFFFF"><strong>Link URL</strong></td>
</tr>

<?php

while ($row=mysqli_fetch_array($result)) {
?>

<tr>
<td align="center" bgcolor="#FFFFFF"><input name="checkbox" type="checkbox" value="<?php echo $row['link_id']; ?>"></td>
<td bgcolor="#FFFFFF"><?php echo $row['link_id']; ?></td>
<td bgcolor="#FFFFFF"><?php echo $row['link_name']; ?></td>
<td bgcolor="#FFFFFF"><?php echo $row['link_url']; ?></td>
</tr>

<?php
}
?>

<tr>
<td colspan="4" align="center" bgcolor="#FFFFFF"><input name="delete" type="submit" value="Delete"></td>
</tr>
<table width="400" border="0" cellspacing="1" cellpadding="0">
<tr>
<td><form name="form1" method="post" action="">
<table width="400" border="0" cellpadding="3" cellspacing="1" bgcolor="#CCCCCC">
 <tr>
<td bgcolor="#FFFFFF">&nbsp;</td>
<td colspan="3" bgcolor="#FFFFFF"><strong>Delete multiple links</strong> </td>
</tr>
<tr>
<td align="center" bgcolor="#FFFFFF">#</td>
<td align="center" bgcolor="#FFFFFF"><strong>Link ID</strong></td>
<td align="center" bgcolor="#FFFFFF"><strong>Link Name</strong></td>
<td align="center" bgcolor="#FFFFFF"><strong>Link URL</strong></td>
 </tr>

<?php

while ($row=mysqli_fetch_array($result)) {
?>

<tr>
<td align="center" bgcolor="#FFFFFF"><input name="checkbox" type="checkbox" value="<?php echo $row['link_id']; ?>"></td>
<td bgcolor="#FFFFFF"><?php echo $row['link_id']; ?></td>
<td bgcolor="#FFFFFF"><?php echo $row['link_name']; ?></td>
<td bgcolor="#FFFFFF"><?php echo $row['link_url']; ?></td>
</tr>

<?php
}
?>

<tr>
<td colspan="4" align="center" bgcolor="#FFFFFF"><input name="delete" type="submit" value="Delete"></td>
</tr>



<?php

// Check if delete button active, start this 

if(isset($_POST['delete']))
{
    $checkbox = $_POST['checkbox'];

for($i=0;$i<count($checkbox);$i++){

$del_id = $checkbox[$i];
$sql = "DELETE FROM links WHERE link_id='$del_id'";
$result = mysqli_query($sql);
}
// if successful redirect to delete_multiple.php 
if($result){
echo "<meta http-equiv=\"refresh\" content=\"0;URL=view_links.php\">";
}
 }

mysqli_close($dbc);

?>

</table>
</form>
</td>
</tr>
</table>

</body>

</html>

This doesn't seem to delete any row. My data is populated in the table. I guess the problem is with the PHP code. Please help me out here.


Solution 1:

You should treat it as an array like this,

<input name="checkbox[]" type="checkbox" value="<?php echo $row['link_id']; ?>">

Then only, you can take its count and loop it for deletion.

You also need to pass the database connection to the query.

$result = mysqli_query($dbc, $sql);

Yours did not include it:

$result = mysqli_query($sql);

Solution 2:

Use array notation like name="checkbox[]" in your input element. This will give you $_POST['checkbox'] as array. In the query you can utilize it as

$sql = "DELETE FROM links WHERE link_id in ";
$sql.= "('".implode("','",array_values($_POST['checkbox']))."')";

Thats one single query to delete them all.

Note: You need to escape the values passed in $_POST['checkbox'] with mysql_real_escape_string or similar to prevent SQL Injection.

Solution 3:

<?php $sql = "SELECT * FROM guest_book";
                            $res = mysql_query($sql);
                            if (mysql_num_rows($res)) {
                            $query = mysql_query("SELECT * FROM guest_book ORDER BY id");
                            $i=1;
                            while($row = mysql_fetch_assoc($query)){
                            ?>


<input type="checkbox" name="checkboxstatus[<?php echo $i; ?>]" value="<?php echo $row['id']; ?>"  />

<?php $i++; }} ?>


<input type="submit" value="Delete" name="Delete" />

if($_REQUEST['Delete'] != '')
{
    if(!empty($_REQUEST['checkboxstatus'])) {
        $checked_values = $_REQUEST['checkboxstatus'];
        foreach($checked_values as $val) {
            $sqldel = "DELETE from guest_book WHERE id = '$val'";
           mysql_query($sqldel);

        }
    }
}