Who thought this was a good idea?

[mrbog]

if (0 == 'asdfasdf' ) echo 'WHAT THE FUCK??????????';

[Chris Hope]

mrbog wrote:

if (0 == 'asdfasdf' ) echo 'WHAT THE FUCK??????????';

I posted something about this the other day.

When comparing a string with a number the string is first evaluated as a
number, which in the case of the above is example is 0. So in effect
you are comparing 0 with 0.

A much safer test is

if(0 === "asdfasdf")

which will evaluate the condition as false. Note I'm using === here and
not ==

=== compares the types strictly whereas == does not.

And yes, I agree it's stupid. Very easy to catch people out.

--
Chris Hope | www.electrictoolbox.com | www.linuxcdmall.com

[Paul Wellner Bou]

Hi,

Chris Hope wrote:

mrbog wrote:

if (0 == 'asdfasdf' ) echo 'WHAT THE FUCK??????????';
I posted something about this the other day.

When comparing a string with a number the string is first evaluated as a
number, which in the case of the above is example is 0. So in effect
you are comparing 0 with 0.

Sorry, this is not correct. The string and the number will be casted to
a boolean value. And a non empty string is definitly true. 0 will be
casted to false.

$ php -r 'if (0 == "asdf") echo "true\n"; else echo "false\n";'
true
if(0 === "asdfasdf")

which will evaluate the condition as false. Note I'm using === here and
not ==

=== compares the types strictly whereas == does not.

This is correct.

$ php -r 'if (0 === "asdf") echo "true\n"; else echo "false\n";'
false

Regards
Paul.

[Michael Winter]

On 11/06/2005 11:35, Paul Wellner Bou wrote:

Chris Hope wrote:

[snip]

When comparing a string with a number the string is first evaluated as a
number, which in the case of the above is example is 0. So in effect
you are comparing 0 with 0.

Sorry, this is not correct.

Unless the documentation is wrong, it certainly is correct.

From Comparison Operators:

"If you compare an integer with a string, the string is converted to
a number."

and from Strings:

"If the string starts with valid numeric data, this will be the value
used. Otherwise, the value will be 0 (zero)."

[snip]

Mike

--
Michael Winter
Replace ".invalid" with ".uk" to reply by e-mail.

[Chris Hope]

Paul Wellner Bou wrote:

Chris Hope wrote:

mrbog wrote:

if (0 == 'asdfasdf' ) echo 'WHAT THE FUCK??????????';

I posted something about this the other day.

When comparing a string with a number the string is first evaluated
as a number, which in the case of the above is example is 0. So in
effect you are comparing 0 with 0.

Sorry, this is not correct. The string and the number will be casted
to a boolean value. And a non empty string is definitly true. 0 will
be casted to false.

It is correct. It's in the manual. Check the first example in the code
block at the following manual page:
http://www.php.net/manual/en/languag...comparison.php

If you were right, then the above code snippet would not output the
text. Try running the code; it *does* output the text.

[rest of comments snipped]

--
Chris Hope | www.electrictoolbox.com | www.linuxcdmall.com

[Oli Filth]

Paul Wellner Bou said the following on 11/06/2005 11:35:

Hi,

Chris Hope wrote:

mrbog wrote:

if (0 == 'asdfasdf' ) echo 'WHAT THE FUCK??????????';

I posted something about this the other day.

When comparing a string with a number the string is first evaluated as a
number, which in the case of the above is example is 0. So in effect
you are comparing 0 with 0.

Sorry, this is not correct. The string and the number will be casted to
a boolean value.

Wha?? Since when does that ever happen? If you did something like:

if (4 == 7) ...

4 and 7 are most definitely *not* converted to Booleans. The same
applies for the example above.
--
Oli

[Paul Wellner Bou]

Chris Hope wrote:

Paul Wellner Bou wrote:

Chris Hope wrote:

When comparing a string with a number the string is first evaluated
as a number, which in the case of the above is example is 0. So in
effect you are comparing 0 with 0.

Sorry, this is not correct. The string and the number will be casted
to a boolean value. And a non empty string is definitly true. 0 will
be casted to false.

It is correct. It's in the manual. Check the first example in the code
block at the following manual page:
http://www.php.net/manual/en/languag...comparison.php

If you were right, then the above code snippet would not output the
text. Try running the code; it *does* output the text.

Sorry... I was confused. Shame on me.
The code sample I gave contradicts my words.

Ignore my post... ;)

Regards
Paul.