how control struct evaluate

[Michael G]

Hi,

$PHONETIC is an array of strings. How can !$PHONETIC['d'], in the case
below, evalutae to true. It is a string not a boolean. It would make more
sense if it evalutated to null.

Thanks Mike

<?php

$PHONETIC = array('a' => 'alpha', 'b' => 'bravo', 'c' => 'charlie');

if(!$PHONETIC['d']):
echo 'true';
else:
echo 'false';
endif

?>


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[jamen]

Michael G wrote:

$PHONETIC is an array of strings. How can !$PHONETIC['d'], in the case
below, evalutae to true. It is a string not a boolean. It would make more
sense if it evalutated to null. $PHONETIC = array('a' => 'alpha', 'b' => 'bravo', 'c' => 'charlie');

Actually, I think it does. Try:

echo @gettype($PHONE TIC['d']);

And when you use NULL in a boolean expression, it evaluates to false

[Michael G]

"jamen" <jamen@invali d> wrote in message
news:42******** *************@d text02.news.tel e.dk...

Michael G wrote:

$PHONETIC is an array of strings. How can !$PHONETIC['d'], in the case
below, evalutae to true. It is a string not a boolean. It would make more
sense if it evalutated to null.

$PHONETIC = array('a' => 'alpha', 'b' => 'bravo', 'c' => 'charlie');

Actually, I think it does. Try:

I know it does, my question is why does it. It seems like an abuse of the
syntax but according to the link below it is not at least in the named
cases.

The following link states a number of cases for boolean conversion. It does
state that an array with zero elements will be converted to FALSE but not
the case above where an array element is not set. Maybe I am reading too
much into it...

http://us2.php.net/manual/en/languag...oolean.casting
Mike

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[Kimmo Laine]

"Michael G" <mi****@montana .com> kirjoitti
viestissä:42*** *******@spool9-west.superfeed. net...

Hi,

$PHONETIC is an array of strings. How can !$PHONETIC['d'], in the case
below, evalutae to true. It is a string not a boolean. It would make more
sense if it evalutated to null.

Thanks Mike

<?php

$PHONETIC = array('a' => 'alpha', 'b' => 'bravo', 'c' => 'charlie');

if(!$PHONETIC['d']):
echo 'true';
else:
echo 'false';
endif

?>

Why would it be a string? It is un undefined variable (undefined array
indexs to be precise). If you call it with a boolean operator, bolean is
assumed, just as well false is assumed since it had no value before. !false
evaluates true quite logically.

$PHONETIC is not an array of strings by no definition. Sure, it contains
three variables that happen to be strings, but that still doesn't meka any
difference. It is simply an array that can hold any kinds of variable types.

There are other tests, that you might find useful. isset() tells you wether
a variable (or array reference) is defined or not. gettype() tells yuo what
is the type of the given variable.

--
SETI @ Home - Donate your cpu's idle time to science.
Further reading at <http://setiweb.ssl.ber keley.edu/>

Soulman <et************ ****@5P4Mgmail. com>

[jamen]

Michael G wrote:

The following link states a number of cases for boolean conversion. It does
state that an array with zero elements will be converted to FALSE but not
the case above where an array element is not set. Maybe I am reading too
much into it...

http://us2.php.net/manual/en/languag...oolean.casting

Well, it clearly states:

When converting to boolean, the following values are considered FALSE:

* the special type NULL (including unset variables)

[Michael G]

"Kimmo Laine" <et************ *******@Mgmail. com> wrote in message
news:dc******** **@phys-news1.kolumbus. fi...

"Michael G" <mi****@montana .com> kirjoitti
viestissä:42*** *******@spool9-west.superfeed. net... <snipped>If you call it with a boolean operator, bolean is
assumed, just as well false is assumed since it had no value before.
!false evaluates true quite logically.

I have to keep reminding myself that php is not typed explicitly but rather
by context. (I think you can set a type though.) I am so used to working
with strongly typed languages. Thanks for your input.

Mike

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[Michael G]

"jamen" <jamen@invali d> wrote in message
news:42******** *************@d text02.news.tel e.dk...

Michael G wrote:

The following link states a number of cases for boolean conversion. It
does state that an array with zero elements will be converted to FALSE
but not the case above where an array element is not set. Maybe I am
reading too much into it...

http://us2.php.net/manual/en/languag...oolean.casting

Well, it clearly states:

When converting to boolean, the following values are considered FALSE:

* the special type NULL (including unset variables)

Thanks. I missed that. Read right over it.
Mike

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