On Thu, 18 Apr 2002, Norman Zhang wrote:
> I am looking at some codes. Some authors use $foo and isset($foo)
> interchangeably. Just to want to make sure that the statement,
>
> if ($foo) { ... }
>
> is different from
>
> if (isset($foo)) { ... }
>
> Right? if ($foo) means variable exists and can be null. Whereas, isset($foo)
> means that the value in $foo cannot be null?
Not quite (or maybe I just don't understand your sentence).
if ($foo)
will be true if $foo has been set to some non-null (and non-zero) value.
It will be false if $foo==null.
On the other hand,
if (isset($foo))
will be true will be true if any value at all has been assigned to $foo,
including null or zero. It will only be false if $foo has never been
assigned in this scope. However, bear in mind that ($foo) will still
evaluate to null even in this case.
miguel
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