<a href="https://x.com/hashtag/PHP?src=hashtag_click" target="_blank" rel="noopener nofollow">#PHP</a> quiz of the day: how can a property be both not set, empty() and failing at comparison with falsy value?
And more than one of us has this bug ATM.
<a href="https://x.com/hashtag/phptip?src=hashtag_click" target="_blank" rel="noopener nofollow">#phptip</a> <a href="https://x.com/hashtag/phptrick?src=hashtag_click" target="_blank" rel="noopener nofollow">#phptrick</a>
<a href="https://php-tips.readthedocs.io/en/latest/tips/not_set_but_exists.html" target="_blank" rel="noopener nofollow">https://php-tips.readthedocs.io/en/latest/tips/not_set_but_exists.html</a>

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A PHP quirk where a class property can simultaneously appear unset, return true for empty(), and fail comparisons with falsy values. This edge case is described as an active bug affecting multiple developers, touching PHP's property initialization and type juggling behavior.

How can a property be not set and still exist?