php function that checks if checkbox is selected. Field validation issue - php

Question

Please read my issue carefully, it's a bit tricky.
The function below is used to display whether a checkbox has been checked in a form on both of my 'add' and 'edit' record pages. No problem here.
The problem:
Let's say I have 2 fields 'name' and 'enabled'. Only fields that is validated is 'name'.
When a user edits an existing record and enters an invalid 'name', the form gets validated. If the user un-checked the 'enabled' checkbox (prior value was $field_record_value="1", setting from the database), the checkbox value still set as "1" as it's still coming from the database.
Question:
How do I get the value to set as "0" when the database record ($field_record_value) is set to 1 ?
I know the issue lies in this code:
$is_checked = isset($field_record_value) ? $field_record_value : '0';
I can't seem to figure it out, maybe because I've spent about 2 hours on this and my brain is fried..but I digress :)
//------------------------------------------------
// Function to check if checkbox is selected
//------------------------------------------------
function form_checkbox_selected($field_name, $page = 'add', $field_record_value = '0')
{
if(!empty($_POST[$field_name]) && intval($_POST[$field_name]))
{
$is_checked = '1';
}
else
{
if($page ==' edit')
{
$is_checked = isset($field_record_value) ? $field_record_value : '0';
}
else
{
$is_checked = '0';
}
}
return $is_checked;
}

Answer 1

The problem is that you are expecting an unchecked value for a checkbox, the browser will never send a value for an unchecked checkbox, so the only way you can know a checkbox is in it's unchecked state is by assumption, which you can only assume after the form has been submitted. I would rewrite your function like so:
function form_checkbox_selected /// line wrapped for SO read-ability
($field_name, $page = 'add', $form_submitted = false, $field_record_value = '0'){
if ( form_submitted ) {
$is_checked = !empty($_POST[$field_name]) ? 1 : 0;
}
else if ( $page == 'edit' ) {
/// isset is not required because it will always
/// be defined by $field_record_value = '0' in default params.
$is_checked = $field_record_value ? 1 : 0;
}
else {
$is_checked = 0;
}
return $is_checked;
}
In order to tell if the form has been submitted or not, it is usually best to have a hidden field that you know will always be sent, or you can define a name for your submit button.
<form>
<input name="sent" type="hidden" value="1" />
</form>
<form>
<input name="sent" type="submit" value="Submit Form" />
</form>
Then on the php side you can call your function:
form_checkbox_selected(
'my_field', 'edit', !empty($_POST['sent']), $db['my_field']
);
This now means your php can make a better assumption of what the field's state is when no data has actually been passed in.