PHPStan is acting weirdly with isset checks when saved into a variable

Bug report

Code snippet that reproduces the problem

https://phpstan.org/r/ef8f3255-41a8-4a83-a55f-7ce9514e8e37

swapping the variable declaration give another issue:
https://phpstan.org/r/6519f526-0ea3-44f9-b811-1c5e797c2983

Expected output

No errors

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