PHP/MySQL Update checkbox selection to database - php

Question

I'm trying to update a database field with a 1 or 0, depending on whether a checkbox is checked or not.
It seems to work when the checkbox is checked but not when empty.
Any ideas how to solve this? Code below. Many Thanks, S.
Here's the code within my form:
$query = "SELECT * FROM istable WHERE assocProp = '".$_POST['id']."'";
$result = mysql_query($query);
while($row = mysql_fetch_array($result, MYSQL_ASSOC))
{
echo '<li>
<label for="changePP'.$row['id'].'"><input id="changePP'.$row['id'].'" type="checkbox" name="showPP_ids[]" value="'.$row['id'].'"'.($row['showPP']=='1' ? ' checked="checked"':NULL).' /> Display</label>
</li>'. PHP_EOL;
}
And the php process code (updated):
$newQuery=mysql_query("select * from ispdfs where assocProp = '".$_POST['id']."'");
$newResult=mysql_fetch_array($newQuery);
foreach ($newResult as $showPP_ids) {
$val = (int) isset($_POST['showPP_ids']);
mysql_query("UPDATE ispdfs SET showPP = $val WHERE id = ".mysql_real_escape_string($showPP_ids));
}

Answer 1

You have nothing here that sets the values to zero. Boxes that are not checked will simply be absent from the $_POST array.
You'll need to make a separate list of the names of all of the checkboxes and cycle through those, comparing them against the $_POST array.
Edit: Wasn't going to write any code, but:
$allids = array('id1','id2','id3');
foreach ($allids as $oneid) {
$val = (int) isset($_POST[$oneid]); // will be 0 or 1
mysql_query("UPDATE istable SET showPP = $val WHERE id = ".mysql_real_escape_string($oneid));
}
Note that we don't really need the mysql_real_escape_string here since we know that all the id values are safe, but it's good practice just in case someone comes along later and carelessly changes the $allids array.
Edit again: Suppose we don't know what ids to look for.
mysql_query("UPDATE istable SET showPP = 0");
foreach ($_POST as $oneid=>$nothing) {
mysql_query("UPDATE istable SET showPP = 1 WHERE id = ".mysql_real_escape_string($oneid));
}

Answer 2

Probably your checkbox value doesn't get sent when it's not checked. Confirm this by print_r($_POST) in your php code.
Because of this, your condition
if (isset($_POST['showPP_ids'])) {
foreach ($_POST['showPP_ids'] as $showPPId) {
will never find a checkbox that wasn't checked.
As awm says correctly (+1 to that), you don't set the field showPP to 0. Do this:
$ppsql=mysql_query("UPDATE istable SET showPP = '0' WHERE id = ".mysql_real_escape_string($showPPId));
when you want to set your sql field to 0.
Since your checkbox won't be sent when it's not checked, you need to have some more information on which checkboxes to expect.
You could do (reusing your query code)
$query = "SELECT * FROM istable WHERE assocProp = '".$_POST['id']."'";
$result = mysql_query($query);
while($row = mysql_fetch_array($result, MYSQL_ASSOC))
{
$found = false;
foreach($_POST['showPP_ids'] as $showPPId)
{
if($showPPId == $row['id'])
{
// checkbox found
$found = true;
break;
}
}
$ppsql=mysql_query("UPDATE istable SET showPP = '"
.($found ? '1' : '0')
."' WHERE id = ".mysql_real_escape_string($showPPId));
}
An alternative would be JavaScript: Provide either two checkboxes and set the "not"-checkbox to true if the other one gets unchecked or use an <input type="hidden"> and change its value when the checkbox gets changed. If you have questions to this method, leave a comment - I've used that some times before...
another approach
Staying with your code, you could use this simple approach (but please don't...):
// first, set all fields to zero
/* long version
$query = "SELECT * FROM istable WHERE assocProp = '".$_POST['id']."'";
$result = mysql_query($query);
while($row = mysql_fetch_array($result, MYSQL_ASSOC))
{
$ppsql=mysql_query("UPDATE istable SET showPP = '0' WHERE id = ".$row['id']);
}
*/
// or short version:
$ppsql=mysql_query("UPDATE istable SET showPP = 0");
// now, update these rows that appear in `$_POST['showPP_ids']`
// (using the code you provided)
if (isset($_POST['showPP_ids'])) {
foreach ($_POST['showPP_ids'] as $showPPId) {
$ppsql=mysql_query("UPDATE istable SET showPP = '1' WHERE id = ".mysql_real_escape_string($showPPId));
}
}