documentation help needed

[William Gill]

I have used and tested the following:

$x = myFunction($som eValue)? "true":"fal se";

When myFunction() returns an empty array, it results in false, and when
it returns a non-empty array it results in true. This is what I want
and expect, but I can't find any documentation on it. Being naturally
cautious (spelled paranoid) I don't want to rely on this until I'm
certain. Can anyone point me to the documentation that supports what
I'm seeing?

[Erwin Moller]

Re: documentation help needed

William Gill schreef:

I have used and tested the following:
>
$x = myFunction($som eValue)? "true":"fal se";
>
When myFunction() returns an empty array, it results in false, and when
it returns a non-empty array it results in true. This is what I want
and expect, but I can't find any documentation on it. Being naturally
cautious (spelled paranoid) I don't want to rely on this until I'm
certain. Can anyone point me to the documentation that supports what
I'm seeing?

Hi,

Why would an empty array evaluate to false?
I don't even know if it does, nor do I care.
Do you want your scripts to rely on such effects?
I wouldn't.

Why not simply write cleanly what you want?

// assuming myFunction always returns an array
$xTemp = myFunction($som eValue);
$x = (count($xTemp) == 0) ? "false" : "true";

Or in case you need true/false as booleans and not as strings:
$xTemp = myFunction($som eValue);
$x = (count($xTemp) 0);

That way somebody else reading your code has also a clue what you are
trying to accomplish.
If you write it in your way, the next person seeing your code will ask
the same questions you are asking yourself now.
That next person could even be yourself in a few years. :P


Regards,
Erwin Moller (clean-code-police)

[Guillaume]

Re: documentation help needed

Erwin Moller a écrit :

// assuming myFunction always returns an array
$xTemp = myFunction($som eValue);
$x = (count($xTemp) == 0) ? "false" : "true";

You may check empty() which directly returns a boolean ^^

Regards,
--
Guillaume

[William Gill]

Re: documentation help needed

Erwin Moller wrote:

>
Why would an empty array evaluate to false?
I don't even know if it does, nor do I care.

It's been a couple of weeks since i tested, but that's what I found.

Do you want your scripts to rely on such effects?
I wouldn't.
>
Why not simply write cleanly what you want?
>
// assuming myFunction always returns an array
$xTemp = myFunction($som eValue);
$x = (count($xTemp) == 0) ? "false" : "true";
>
Or in case you need true/false as booleans and not as strings:
$xTemp = myFunction($som eValue);
$x = (count($xTemp) 0);
>
That way somebody else reading your code has also a clue what you are
trying to accomplish.
If you write it in your way, the next person seeing your code will ask
the same questions you are asking yourself now.
That next person could even be yourself in a few years. :P

Actually I am emulating someone else's code. My example was rewritten
to focus on the true/false value of the assignment operation. In
practice it reads more like:

if($errors=chec kForErrors(){
/* there are errors, do something about it */
else{
/* no errors so do something else*/
}

}

[William Gill]

Re: documentation help needed

Guillaume wrote:

You may check empty() which directly returns a boolean

That insures a reliable true/false test.

It also helps with a previous concern regarding the $_POST array.

Thanks.

[William Gill]

Re: documentation help needed

Erwin Moller wrote:

Why would an empty array evaluate to false?
I don't even know if it does, nor do I care.

I retested and both an empty array and an assignment of an empty array
return false.

As stated elsewhere, the code I'm emulating uses the true/false result
of the assignment to control flow, but as Guillaume points out, empty()
is more explicit (and probably more reliable).

[Michael Fesser]

Re: documentation help needed

..oO(Erwin Moller)

>William Gill schreef:

>I have used and tested the following:
>>
>$x = myFunction($som eValue)? "true":"fal se";
>>
>When myFunction() returns an empty array, it results in false, and when
>it returns a non-empty array it results in true. This is what I want
>and expect, but I can't find any documentation on it. Being naturally
>cautious (spelled paranoid) I don't want to rely on this until I'm
>certain. Can anyone point me to the documentation that supports what
>I'm seeing?

>
>Why would an empty array evaluate to false?
>I don't even know if it does, nor do I care.

It does by definition, see PHP's type juggling. All these values
evaluate to FALSE if casted to boolean:

0, '0', array(), '', NULL

>Do you want your scripts to rely on such effects?
>I wouldn't.

I wouldn't either usually, but for another reason. An explicit test is
cleaner and more readable code.

Micha

[William Gill]

Re: documentation help needed

Michael Fesser wrote:

>
It does by definition, see PHP's type juggling. All these values
evaluate to FALSE if casted to boolean:
>
0, '0', array(), '', NULL

Thanks, that's the type of documentation I was looking for.

>

>Do you want your scripts to rely on such effects?
>I wouldn't.

>
I wouldn't either usually, but for another reason. An explicit test is
cleaner and more readable code.

Agreed. Using an explicit call to empty() is clearer, but sometimes
using a multi step to feed a conditional may be counter productive.

function setClass($field name){
global $form_errors;
if(isset($form_ errors)) {
return array_key_exist s('$fieldname', $form_errors) ? 'error' :
'normal'; /*set css class */
}
else{return 'normal';}
}
....
....
....

<input name="First_Nam e" type="text"
class="<?php echo setClass('First _Name') ?>"
value="<?php echo getVal('First_N ame') ?>" size="20">

[William Gill]

Re: documentation help needed

William Gill wrote:

>
function setClass($field name){
global $form_errors;
if(isset($form_ errors)) {
return array_key_exist s('$fieldname', $form_errors) ? 'error' :
'normal'; /*set css class */
}
else{return 'normal';}
}
...
...
...
>
<input name="First_Nam e" type="text"
class="<?php echo setClass('First _Name') ?>"
value="<?php echo getVal('First_N ame') ?>" size="20">
>

Disregard my example, it is completely off base (I was distracted / had
my head up my... well, you know what I mean).

[Gordon]

Re: documentation help needed

On May 26, 2:50 pm, William Gill <nore...@exampl e.comwrote:

I have used and tested the following:
>
$x = myFunction($som eValue)? "true":"fal se";
>
When myFunction() returns an empty array, it results in false, and when
it returns a non-empty array it results in true.  This is what I want
and expect, but I can't find any documentation on it.  Being naturally
cautious (spelled paranoid) I don't want to rely on this until I'm
certain.  Can anyone point me to the documentation that supports what
I'm seeing?

That's very odd behavior you're getting there, I was under the
impression that empty arrays evaluated to true! For that reason, I'd
consider being a bit more thorough in checking what you get back from
your function to make sure it really is what you think it is. I could
be mistaken on that front of course, I'd have to check the
documentation on what evaluates to true and what doesn't, but
personally I'd be running count() on your function's return value and
checking it was greater than 0.

[Lars Eighner]

Re: documentation help needed

In our last episode, <Do6dna5hJ5OLXa fVnZ2dnUVZ_qvin Z2d@wideopenwes t.com>,
the lovely and talented William Gill broadcast on comp.lang.php:

I have used and tested the following:

$x = myFunction($som eValue)? "true":"fal se";

When myFunction() returns an empty array, it results in false, and when
it returns a non-empty array it results in true. This is what I want
and expect, but I can't find any documentation on it.

'Comparison Operators' in the "Operators" section of the manual -- Chapter
15 in my version. Or simply grep the manual for 'ternary operator' --- I
don't think there is another one.

Being naturally cautious (spelled paranoid) I don't want to rely on this
until I'm certain. Can anyone point me to the documentation that supports
what I'm seeing?

--
Lars Eighner <http://larseighner.com/usenet@larseigh ner.com
Countdown: 238 days to go.

[Michael Fesser]

Re: documentation help needed

..oO(Gordon)

>On May 26, 2:50 pm, William Gill <nore...@exampl e.comwrote:

>I have used and tested the following:
>>
>$x = myFunction($som eValue)? "true":"fal se";
>>
>When myFunction() returns an empty array, it results in false, and when
>it returns a non-empty array it results in true.  This is what I want
>and expect, but I can't find any documentation on it.  Being naturally
>cautious (spelled paranoid) I don't want to rely on this until I'm
>certain.  Can anyone point me to the documentation that supports what
>I'm seeing?

>
>That's very odd behavior you're getting there, I was under the
>impression that empty arrays evaluated to true!

It's correct behaviour, empty always arrays evaluate to FALSE.

Converting to boolean

http://www.php.net/manual/en/language.types.boolean.php#language.types.boolean.casting

Micha

[Michael Fesser]

Re: documentation help needed

..oO(Gordon)

>On May 26, 2:50 pm, William Gill <nore...@exampl e.comwrote:

>I have used and tested the following:
>>
>$x = myFunction($som eValue)? "true":"fal se";
>>
>When myFunction() returns an empty array, it results in false, and when
>it returns a non-empty array it results in true.  This is what I want
>and expect, but I can't find any documentation on it.  Being naturally
>cautious (spelled paranoid) I don't want to rely on this until I'm
>certain.  Can anyone point me to the documentation that supports what
>I'm seeing?

>
>That's very odd behavior you're getting there, I was under the
>impression that empty arrays evaluated to true!

It's correct behaviour, empty arrays always evaluate to FALSE.

Converting to boolean

http://www.php.net/manual/en/language.types.boolean.php#language.types.boolean.casting

Micha

[AnrDaemon]

Re: documentation help needed

Greetings, William Gill.
In reply to Your message dated Monday, May 26, 2008, 19:16:51,

Erwin Moller wrote:

>Why would an empty array evaluate to false?
>I don't even know if it does, nor do I care.

I retested and both an empty array and an assignment of an empty array
return false.

They are values that assumed as "empty" (no data) for comparison.
These are - "false" value, numerical zero, empty string, the NULL constant,
empty array.
To make sure you are using true/false test, use strict type comparison (the
=== or !== operators).
Then the

$arr = array();
if(false !== $arr)
{
print('it is not \'false\' value');
}

will show you the truth. Empty array is not the same as 'false' value.

As stated elsewhere, the code I'm emulating uses the true/false result
of the assignment to control flow, but as Guillaume points out, empty()
is more explicit (and probably more reliable).

For your specific needs probably, but make sure your functions returning
true/false results, before using them in flow control.
In some cases, you may want to return zero as valid result, and that will
ruine your empty($result) check.


--
Sincerely Yours, AnrDaemon <anrdaemon@free mail.ru>