How can I tell the difference between a variable whose value is null and
a variable which is not set?

// cannot use === null:

ket% php -r '$null = null; var_dump(null === $null);'
bool(true)
ket% php -r 'var_dump(null === $unset);' bool(true) ket%
// - cannot use isset() either:

ket% php -r '$null = null; var_dump(isset($null));' bool(false) ket% php -r 'var_dump(isset($unset));' bool(false) ket%


Although this is a good problem to lose time for I think it is pointless. Since assigning the null constant to a var is making PHP to pretend like it never existed.

Is this not the point?

Without this feature I can think many cases that isset or is_null would be useless.

You could always assign to something the empty string '' and use empty() to check it as an alternative.

BTW what are you trying to do?

--
Thodoris


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