Re: In php 8.0: unable to distinguish between instance variable being null and unset

Hey Emiel, On Fri, Sep 3, 2021 at 3:09 PM Emiel Mols <emiel@crisp.nl> wrote: > Hello, > > Our codebase depends on distinguishing whether an instance variable is > unset, or simply null: > Can you please share more on how you use this information? Is it for lazy loading something that might not be loadable in the end? > > class C { public int $v = 123; } > $x = new C; unset($x->v); > $y = new C; $u->v = null; > > In php <8.0 we made this work with @array_key_exists($x, 'v'), which > stopped working. isset($x->x) doesn't work, as it will return true for > 'null' as well. property_exists($x, 'v') will always return true as long as > the variable is declared: php-src here > > <https://github.com/php/php-src/blob/a13730c5e465b3c349a7970d15a49e4e132d4e07/Zend/zend_builtin_functions.c#L943> > . > > Apart from using debug_zval_dump (too expensive), any hints? > I think the simplest solution would be to cast the object to an array and you will see that the unset property will not be a key in the array while the null one will be. Another way to go here would be to use the magic method __get() that would be called on the unset property. But not sure how that fits with your use case. Also something like this could work: https://3v4l.org/7NL0Y, trying to read the property and handling the Error thrown. But it all depends on how you use this... Please share more to help you correctly. > This feels like quite the oversight honestly :). > This feels like quite a special use case that could be implemented differently to start with. Please share more information so we can help better. I guess you have read the rfc that deprecated this in 7.4 and scheduled for later removal: https://wiki.php.net/rfc/deprecations_php_7_4#array_key_exists_with_objects > > Best, > > Emiel > Alex