Question

I want to select multiple rows from checkbox and want to update them all at once by button click..I tried in several ways..but not work..can you give a help please? it shows an error as Undefined index: checkbox

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

if(isset($_POST['send_btn']) and $_POST['send_btn']=="Send"){
    $checkbox = $_POST['checkbox']; //from name="checkbox[]"
    $countCheck = count($_POST['checkbox']);

    for($i=0;$i<$countCheck;$i++){
        $del_id = $checkbox[$i];
        $sql2 = "UPDATE retained_file_mst SET mark_to_dispose=1 WHERE file_serial_id='$del_id'";
        $result2 = mysql_query($sql2,$conn);
    }

    // if successful redirect to delete_multiple.php
    if($result2){
        echo "success";
    }else{
        echo "error";
    }
}

Answer 1

You can access your checkboxes like so:

$checkbox = isset($_POST['checkbox']) ? $_POST['checkbox'] : 0;

This allows you to set it to the correct value if the user entered it and set it to 0 if the user did not check it.

Another alternative would be to set it 0 which may be more space conservative for things like databases.

Edit

Since you are actually using it as an array this would be better:

$checkbox = isset($_POST['checkbox']) ? $_POST['checkbox'] : array();

Or just doing a quick if to see if the $checkbox is an array:

if(is_array($checkbox)){
    // do the for statement
}

P.S Use code formatting if you want people to understand your question. I have done it for you this time