Comments on: Don’t use “and” and “or” logical operator in PHP, it has flaw

By: Pooja

Pooja — Wed, 23 Dec 2009 06:23:47 +0000

The basic logic for using the logical operators in any of language especially works same as the semiconductor Gates.If anyone who is aware of semiconductors gates ,then he/she can truely can say that this is not an flaw.
this is the And Gate truth table
INPUT OUTPUT
A B A AND B
0 0 0
0 1 0
1 0 0
1 1 1

and this is the or gate truth table

INPUT OUTPUT
A B A OR B
0 0 0
0 1 1
1 0 1
1 1 1

if 1 is true and 0 is false
then tracing accordingly ,will find that PHP returns the correct answer.So I guess,its not a flaw…..

By: svnlabs

svnlabs — Tue, 03 Nov 2009 19:00:42 +0000

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Awesome!!
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svnlabs

By: Matt

Matt — Fri, 13 Mar 2009 14:34:15 +0000

The logical operators work fine in PHP when you use sound logic to test them. I use them all the time. As Khalid said, not understanding precedence is not a “flaw” in php, it is a lack of understanding on your part. Khalid should have updated his “prints” comments on the code he posted like so.

$return_val = (false or true);
var_dump($return_val); //prints bool(true)

$return_val = (true and false);
var_dump($return_val); //prints bool(false)

Again, basic logic… not a flaw… I hope you have not confused the crap out of anyone else with this.

By: jimmy

jimmy — Wed, 31 Dec 2008 06:00:55 +0000

maybe this flaw in individually release of php

By: What The Heck Is PHP? : ProfitableSistas

What The Heck Is PHP? : ProfitableSistas — Thu, 28 Aug 2008 06:10:34 +0000

[...] Don’t use “and” and “or” logical operator in PHP, it has flaw – Today, When I was doing some programming stuffs and I found out that there is serious flaw in the “and” , “or” logical operator of PHP. I’m not talking about the symbol “||” and “&&” logical operator. I’m talking about the “and” and … Share and Enjoy: [...]

By: Roshan

Roshan — Sat, 21 Jun 2008 15:20:02 +0000

ya U saw that link…as you can see you can see the undesired result due to precedence of the operator…

By: khalid

khalid — Thu, 19 Jun 2008 05:18:20 +0000

My PHP version is “5.2.6″.
We need to go through the below link.

http://in.php.net/manual/en/language.operators.logical.php

By: Roshan

Roshan — Thu, 19 Jun 2008 04:33:17 +0000

hey Khalid….which PHP version u’re using? I’m using PHP5 and the above result is absolutely correct, I’ve tested it 3-4 times in PHP5…
better check your result once man….

By: khalid

khalid — Wed, 18 Jun 2008 21:12:01 +0000

the above commented result is wrong, i think u got the funda.

By: khalid

khalid — Wed, 18 Jun 2008 21:06:56 +0000

$return_val = (false or true);
var_dump($return_val); //prints bool(false)

$return_val = (true and false);
var_dump($return_val); //prints bool(true)

By: khalid

khalid — Wed, 18 Jun 2008 21:04:07 +0000

Use logical AND and OR operator always in brackets ( ) , it will give you the proper result.
PHP does not have any flaws regarding it.

Your code should be like this :

Enjoy !

By: Roshan

Roshan — Tue, 17 Jun 2008 16:18:39 +0000

@Bijay – Thanks man…I’ve just using it and got this undesired result and wanted alert everyone..

@Alexa – thanks for explanation…a beginner developer may really be in dilemma if they use the example in the way I did..the priority of “and” , “or” operator is really awful compared to assignment operator…

By: Alex@Net

Alex@Net — Tue, 17 Jun 2008 11:58:33 +0000

Priotiry of the OR operator is less then =.
So $return_val = false or true; will be evaluated as: ($return_val = false) or true;
OR is usefull when you need to write something like this:
$var = $var1 or $var = $var2 or $var = $var3;
which is a shortcut to:
if ($var1) $var = $var1 elseif ($var2) …

By: Bijay Rungta

Bijay Rungta — Tue, 17 Jun 2008 10:28:46 +0000

Cool Stuff..
Good that I never used them as far as I can remember…

I dug this Story..

http://digg.com/programming/Flaw_in_and_and_or_logical_operator_in_PHP