At 03:02 AM 2/7/2001 +0100, Cynic wrote:
>with all respect to the people who develop the language, I
>think this is nonsense:
>
>$rs = mysql_query( 'select x, y, z from foo where ...' ) ;
>$x = mysql_fetch_array( $rs , MYSQL_NUM ) ;
>var_dump( $x[2] ) ;
>var_dump( isset( $x[2] ) ) ;
>
>NULL # well, the column contains null values
>bool(false)
>
>But since (almost) everybody else disagrees, I must be missing
>something obvious.
>
>BTW, does $x = null really equal to unset( $x ) or does
>isset() just get fooled by its value?
unset() removes it from the symbol table and $x = NULL; changes it to be a
NULL value. As far as PHP scripts are concerned it's pretty much the same
thing. There are certain situations where you can't really nuke the
variable but you want to mark it as dead.
In any case, you can always use the === operator to check if something is
really NULL and not false.
if ($x === NULL) {
}
I can't remember off hand all the reasons for isset(NULL) being false but
the main reason is that it makes a lot of sense because what the NULL value
is supposed to mean is that there's no value. Also it allows us to
differentiate between functions returning bool(false) and null values.
Hence also the === operator.
I really think that if your script differentiates between these two cases
you might not be writing it very well.
OK, I know it's a messy Email. I'm on the way to bed but I hope it
clarifies a few things :)
Andi
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