update multiple checkbox data by using loop - php

Question

There are multiple checkbox about 50+ for user access, checkbox are like follows;
<input name="PREFIX_1" type="checkbox">
<input name="PREFIX_2" type="checkbox">
<input name="PREFIX_3" type="checkbox">
...........
I have multiple checkbox with its respective values which I loop through to add/update the values in the database, which is like follows:
foreach ($_POST as $field => $value ) {
if ( preg_match('/^PREFIX_/', $field) ) {
$access = isset($value)?'1':'0';
$file = substr($field, 4);
$this->db->query('UPDATE_DESIRED_TABLE');
}
}
The problem is when I add/update the values in the database by using loop foreach ($_POST as $field => $value ) and checking the prefix, I only get values of checkbox that are checked and the values of data that are not checked are not in the $_POST data.
And, I don't get any values which are not checked, which is not even the name of that checkbox. In other words only those values are set which are checked.
Now I have to change the value of all the data in the database by comparing both the data in the database and from the post data.
How can I solve this?

Answer 1

You would need to send hidden inputs along with the checkboxes like this:
<form action="" method="post">
<input type="hidden" id="PREFIX_1_" name="PREFIX_1" value="0">
<input type="checkbox" id="PREFIX_1" name="PREFIX_1" value="1" />
<input type="hidden" id="PREFIX_2_" name="PREFIX_2" value="0">
<input type="checkbox" id="PREFIX_2" name="PREFIX_2" value="1" />
<input type="hidden" id="PREFIX_3_" name="PREFIX_3" value="0">
<input type="checkbox" id="PREFIX_3" name="PREFIX_3" value="1" />
<input type="submit" name="sub" value="Go" />
</form>
However you cant use the isset anymore with this, change PHP like this:
if(isset($_POST['sub']))
{
foreach ($_POST as $field => $value )
{
if ( preg_match('/^PREFIX_/', $field) )
{
$access = $value;
$file = substr($field, 4);
$this->db->query('UPDATE_DESIRED_TABLE');
}
}
}

Answer 2

Considering you know the number of checkbox, stored in example in $checkBoxCount, you might use this kind of loop :
for ($i = 1; $i <= $checkBoxCount; $i++)
{
$access = ((isset($_POST["PREFIX_" . $i])) ? ('1') : ('0')));
//manage DB
}