question about php operator

[lukelee]

I am confusing about the php operator, are these 2 if conditions the same?

if(($filesize1 && $filesize2 && $filesize5 != 0) && ($filesize3 ==0)&& ($filesize4 ==0))

 

if(($filesize1 && $filesize2 && $filesize5 != 0) && ($filesize3 && $filesize4 ==0))

[PFMaBiSmAd]

The distributive property is only valid in algebra, not in programming logic - http://www.icoachmath.com/SiteMap/DistributiveProperty.html

[Mchl]

The distributive property is only valid in algebra, not in programming logic - http://www.icoachmath.com/SiteMap/DistributiveProperty.html

 

It's as valid in programming, as it is in algebra.

$a && ($b || $c) == ($a && $b) || ($a && $c)

 

But!

 

$filesize3 && $filesize4 == 0 is not the same as ($filesize3 == 0) && ($filesize4 == 0) and I believe lukelee is after the second one.

 

$filesize3 && $filesize4 == 0 first evaluates $filesize3 && $filesize4 and then compares the result to 0

 

[lukelee]

The distributive property is only valid in algebra, not in programming logic - http://www.icoachmath.com/SiteMap/DistributiveProperty.html

 

It's as valid in programming, as it is in algebra.

$a && ($b || $c) == ($a && $b) || ($a && $c)

 

But!

 

$filesize3 && $filesize4 == 0 is not the same as ($filesize3 == 0) && ($filesize4 == 0) and I believe lukelee is after the second one.

 

$filesize3 && $filesize4 == 0 first evaluates $filesize3 && $filesize4 and then compares the result to 0

 

 

the second one is to compare$filesize3 and $filesize4, does that mean $filesize3 == $filesize4?

[GingerRobot]

$filesize3 && $filesize4 == 0 first evaluates $filesize3 && $filesize4 and then compares the result to 0

 

Not quite. The == operator has a higher precedence than the && operator. Therefore, $filesize3 would first be evaluated, then $filesize4 == 0 would be evaluated assuming $filesize3 is true, owing to shortcut evaluation.

[Mchl]

Not quite. The == operator has a higher precedence than the && operator. Therefore, $filesize3 would first be evaluated, then $filesize4 == 0 would be evaluated assuming $filesize3 is true, owing to shortcut evaluation.

 

That's why I overuse () in conditions