about the | or || operator

[sfullman]

Hi There,

this code:

function returnit($val){
	if($val==6){ echo 'oops!'; exit; }else{ return $val; }
}
//now execute the | logical operator
if($a=returnit(5) | $a=returnit(6)){
	echo $a;
}

Doesn't echo 5, it's obvious that BOTH logical conditions are checked.

HOWEVER, this code:

function returnit($val){
	if($val==6){ echo 'oops!'; exit; }else{ return $val; }
}
//now execute the || logical operator
if($a=returnit(5) || $a=returnit(6)){
	echo $a;
}

Doesn't echo 5, instead it echos 1.

Now finally, this code:

function returnit($val){
	if($val==6){ echo 'oops!'; exit; }else{ return $val; }
}
//now execute the OR logical operator
if($a=returnit(5) OR $a=returnit(6)){
	echo $a;
}

Echos 5 like I'd expect (BTW I never write out OR anymore before this).

What's driving me crazy is, why is the second case with the || short circuiting like it's supposed to but the echo value turns to 1? I use || a lot in my code, very rarely for short-cicuiting, but would like to understand the language.

By the way I did search through the PHP documentation and I couldn't find anything on this.

Sam

[laserlight]

That's because || is a logical OR operator, while | is a bitwise OR operator.

[swr]

First of all, | (single vertical bar) is a bitwise OR. It uses the binary representation of both numbers, and returns another number for which every bit that was set in either of the two inputs will be set in the resulting output. You almost never want this. It has (almost) nothing to do with || or OR.

The difference between || and OR is precedence. This:

$a=returnit(5) || $a=returnit(6)

is the same as this:
$a=(returnit(5) || $a=returnit(6))

That is, $a is set to the boolean true/false'ness of the expression. That's why you get 1.

On the other hand, this:
$a=returnit(5) OR $a=returnit(6)

is the same as this:
($a=returnit(5)) OR ($a=returnit(6))

So $a gets set to 5.

See operator precedence:

http://www.php.net/manual/en/language.operators.php#language.operators.precedence

[edit]
Actually, I think this:
$a=returnit(5) || $a=returnit(6)
should be the same as this:
$a=(returnit(5) || $a)=returnit(6)
which should be an error...?

[few-time-poster]

Maybe it's because it's real late right now, but I'm having the same kind of problem:

What I'm trying to do is to check the "Month when trip begins" (LMonth) versus the "Month that the trip ends".(RMonth)

I want it so that if the user puts in January for the Leaving month and then puts in a month OTHER than February or March, he'll get an error message. -->He can only use "February" or "March" as the month the trip ends, anything else gets an error message.

This does NOT work:

if(($LMonth=="January" && $RMonth!="February") OR ($LMonth=="January" && $RMonth!="March")){
echo "Invalid date---months are out of order";
exit;
}else{

whereas this DOES:

if($LMonth=="January" && $RMonth!="February"){
echo "Invalid date---months are out of order";
exit;
}else{

[PHPMagician]

Try:

if ($LMonth == 'January' && ($RMonth != 'February' && $RMonth != 'March')) {
    exit("Invalid Return Months");
}

[PHPMagician]

If you ever do, for some reason, want the || to return the value returned by the function, just do it like:

<?php
function returnit($val){
    if($val==6){ echo 'oops!'; exit; }else{ return $val; }
}
//now execute the || logical operator
if(($a=returnit(5)) || ($a=returnit(6))){
    echo $a;
}
?>

The right combination of parentheses usually helps reach the desired goal.