value '0' is quite common,
the checks empty($value) and empty($value[0]) should be changed

I'm also not sure if strlen is the solution as asked here #19753 (comment).

I'm also not sure if strlen is the solution as asked here

well, $value can not be an object, it is either
null, boolean, string, or array

null, boolean, string are all of them 'valid' inputs for strlen

so the only check that needs to be made is that $value and $value[0] are not an array

consider "empty" if
is_array($value) ? !count($value) : !strlen($value)
the above should replace empty($value)

is_array($value[0]) ? !count($value[0]) : !strlen($value[0])
the above should replace empty($value[0])

I have tested this item ✅ successfully on 5db8f95

Tested on both com_content and com_user (back-end and front-end)

1. saving with empty checkbox removes checkbox previous value from table = OK
2. removing value from field removes value from table = OK
3. setting field to only display on administrator and the save article or user on front-end retains value for the field in the table = OK
4. changing user groupmembership via API retains field values for this user = OK

pinging @Denitz , @joomdonation , @ggppdk on this PR.

I have been trying to test for all your (related) issues and I think that they are fixed with this PR.
Can you test as well so we can get 'the show on the road' :)

Also calling on @tassosm and @regularlabs as I know they develop custom fields and (could) have an interest in also getting this fixed :)

@laoneo As @ggppdk has commented, the value of 0 will be cleared and not saved which I have confirmed.

Added the proposal from @ggppdk. Can you guys please test again?

Hi @laoneo , it fails :(
I have a text field and a checkbox field. It only saves one of them: when changing the checkbox, then the text field is deleted and vv. reverting $needsDelete in 9c68d5b fixes it ($needsDelete = empty($value[0]);)

EDIT: fixed this via new PR against your repo

Hi @laoneo just did two PR's against your repo.
with these PR's it is possible to save value 0 as actual value AND it corrects the incorrect behaviour on single character text values (strlen = 1)

Now clicking the Save button two times will clear entered values.

@Quy could you try this: Digital-Peak#12
That should fix it.

@Ruud68 Fixed. Thank you!

Ok please let me explain things
the empty() check was in 2 places
now both are patched

but

@Ruud68

It was:

$needsUpdate = !empty($value[0]);

It was patched to be

$needsUpdate = is_array($value[0]) ? !count($value[0]) : !strlen($value[0]);

The negation was of !empty($value[0])

• was lost

Now clicking the Save button two times will clear entered values.

that is why it is not working !

the complex expression that you suggest in your PR fixes it but it is not needed be like that,
you are just readding the negation back with a more complex expression

so just re-add the negation:

$needsUpdate = ! (is_array($value[0]) ? !count($value[0]) : !strlen($value[0]));
//or better
$needsUpdate = is_array($value[0]) ? count($value[0]) : strlen($value[0]));

the complex expression that you suggest in your PR fixes it but it is not needed be like that,
you are just readding the negation back with a more complex expression

Agree and @laoneo already simplified that. the code I suggested was a quick-mockup from me trouble shooting where things went wrong :)

With this last PR Digital-Peak#12 it works :)
with your code:

$needsUpdate = is_array($value[0]) ? count($value[0]) : strlen($value[0]);

When this PR is committed I will be re-doing all my test cases (which are already a lot :))

Pr's from @Ruud68 got merged.

I have tested this item ✅ successfully on 2756bb8

Tested on both com_content and com_user (back-end and front-end)

1. saving with empty checkbox removes checkbox previous value from table = OK
2. removing value from field removes value from table = OK
3. setting field to only display on administrator and the save article or user on front-end retains value for the field in the table = OK
4. changing user groupmembership via API retains field values for this user = OK
5. saving value of 1 character saves okay
6. saving value 0 saves okay

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Pr's from @Ruud68 got merged.

all credits for my last PR's go to @ggppdk. Some say they where inspired, I just copied his code :)))

@Quy and @ggppdk can you find some time to test and if okay approve?

I have tested this item ✅ successfully on 2756bb8

RTC