Question

Assuming a situation like this, a page with simple form input phone number and it allow multi user – access:

<form>
Name: * <input type="text" name="name" /><br />
Phone: (if any) <input type="text" name="phone" /><br />
</form> 

The phone field in database is pre-defined as allow-null.
The problem is when user A inputting the form , user B modify the database and set phone field as not-null . When user A submit , the phone will be a null value and post to the mysql database.

What i want to achieve is , if that field is modifyied to non-null, it should refresh before submit, retrieve the database structure before submit. Once there is difference, it return to the form and display like the following

<form>
Name: * <input type="text" name="name" /><br />
Phone: * <input type="text" name="phone" /> Sorry. You have to enter phone number<br />
</form> 

How can it implement base on php(if possible)/ ajax? Thanks for the help.

Answer 1

Its quite weird to implement any refresh before submit and make decisions on browser side.

Such a situation should be checked on PHP side (after submit), which should return an error result-code meaning “The field is not null any more, please provide a value”