PHP boolean's

[Michael Sharman]

Can anyone confirm if in PHP 0 = FALSE and anything else if TRUE?

Or is it more 0 = FALSE and 1 = TRUE?

One of the reasons I ask is that if I do;

//$count is an incrementing value starting from 0 in a loop
if($count % 2)
{
//do something
}

This works fine, but if I do:
if(!$count % 2)
{
//do something
}

It doesn't work. Should it not just be a boolean comparison? Why do I
need to do this to get my FALSE?

if($count % 2 === 0)
{

}

[petersprc]

The not operator (!) has higher precedence and is evaluated prior to
the mod operator.

You can use: if ($count % 2 == 0)

Precedence list:

http://us.php.net/manual/en/language...ors.precedence

As for your other question about boolean comparisons, here are the
rules on boolean conversion:

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

Regards,

John Peters

On May 30, 9:38 pm, Michael Sharman <[e-mail]:

Can anyone confirm if in PHP 0 = FALSE and anything else if TRUE?

Or is it more 0 = FALSE and 1 = TRUE?

One of the reasons I ask is that if I do;

//$count is an incrementing value starting from 0 in a loop
if($count % 2)
{
//do something

}

This works fine, but if I do:
if(!$count % 2)
{
//do something

}

It doesn't work. Should it not just be a boolean comparison? Why do I
need to do this to get my FALSE?

if($count % 2 === 0)
{

}

[Michael Sharman]

On May 31, 11:57 am, petersprc <[e-mail]:

The not operator (!) has higher precedence and is evaluated prior to
the mod operator.

You can use: if ($count % 2 == 0)

Precedence list:

http://us.php.net/manual/en/language...uage.operators...

As for your other question about boolean comparisons, here are the
rules on boolean conversion:

http://us2.php.net/manual/en/languag...#language.type...

Regards,

John Peters

On May 30, 9:38 pm, Michael Sharman <[e-mail]:

Can anyone confirm if in PHP 0 = FALSE and anything else if TRUE?

Or is it more 0 = FALSE and 1 = TRUE?

One of the reasons I ask is that if I do;

//$count is an incrementing value starting from 0 in a loop
if($count % 2)
{
//do something

}

This works fine, but if I do:
if(!$count % 2)
{
//do something

}

It doesn't work. Should it not just be a boolean comparison? Why do I
need to do this to get my FALSE?

if($count % 2 === 0)
{

}

Thanks for that John.

I suppose I can also do;

if(!($count % 2))

[Michael Fesser]

..oO(Michael Sharman)

>I suppose I can also do;

if(!($count % 2))

Yes. But even if this is documented behaviour, it's usually recommended
to explicitly write what you want to test for. In this case you're not
testing a boolean value ('!' is a logical operator), but an arithmetic
expression. So you should better write it as

if ($count % 2 == 0) {
...
}

This is cleaner and more readable code. Another example: The typical
shorthand way for testing if an array is empty or not is

if (!$someArray) {
...
}

But the better way is

if (empty($someArray)) {
...
}

Micha

[Rik Wasmus]

On Sat, 31 May 2008 14:31:51 +0200, Michael Fesser <ne*****@gmx.dewrote:

.oO(Michael Sharman)

>I suppose I can also do;

if(!($count % 2))

Yes. But even if this is documented behaviour, it's usually recommended
to explicitly write what you want to test for. In this case you're not
testing a boolean value ('!' is a logical operator), but an arithmetic
expression. So you should better write it as

if ($count % 2 == 0) {
...
}

This is cleaner and more readable code. Another example: The typical
shorthand way for testing if an array is empty or not is

if (!$someArray) {
...
}

But the better way is

if (empty($someArray)) {
...
}

One could even argue using if(count($someArray) == 0) is better, as
empty() will not only work for arrays , but for a whole list of empty
values ('',0,null, etc.). Using the count function does immediatly issue
an error (non-fatal) when $someArray is not an array, making it more easy
to track bugs and errors. That being, said, I usually do use empty()
though :).
--
Rik Wasmus
....spamrun finished

[Michael Fesser]

..oO(Rik Wasmus)

>One could even argue using if(count($someArray) == 0) is better, as
empty() will not only work for arrays , but for a whole list of empty
values ('',0,null, etc.). Using the count function does immediatly issue
an error (non-fatal) when $someArray is not an array, making it more easy
to track bugs and errors. That being, said, I usually do use empty()
though :).

ACK

The only annoying thing (IMHO) about empty() is that it only works on
variables, but sometimes I want to directly check a function result.
So I had to write a little helper function:

function isEmpty($var) {
return empty($var);
}

Now I can do things like

if (isEmpty(getSomething())) {
...
}

where the normal empty() would complain.

Micha

[Michael Sharman]

On May 31, 10:31 pm, Michael Fesser <[e-mail]:

.oO(Michael Sharman)

I suppose I can also do;

if(!($count % 2))

Yes. But even if this is documented behaviour, it's usually recommended
to explicitly write what you want to test for. In this case you're not
testing a boolean value ('!' is a logical operator), but an arithmetic
expression. So you should better write it as

if ($count % 2 == 0) {
...

}

This is cleaner and more readable code. Another example: The typical
shorthand way for testing if an array is empty or not is

if (!$someArray) {
...

}

But the better way is

if (empty($someArray)) {
...

}

Micha

Thanks Michael, that's a solid response

[Curtis]

Michael Sharman wrote:

On May 31, 10:31 pm, Michael Fesser <[e-mail]:

>.oO(Michael Sharman)

>>I suppose I can also do;
if(!($count % 2))

Yes. But even if this is documented behaviour, it's usually recommended
to explicitly write what you want to test for. In this case you're not
testing a boolean value ('!' is a logical operator), but an arithmetic
expression. So you should better write it as

if ($count % 2 == 0) {
...

}

This is cleaner and more readable code. Another example: The typical
shorthand way for testing if an array is empty or not is

if (!$someArray) {
...

}

But the better way is

if (empty($someArray)) {
...

}

Micha

Thanks Michael, that's a solid response

Some additional info on type comparison:

<URL:http://php.net/manual/en/types.comparisons.php>

--
Curtis