using AND instead of IF

[siriushoward]

Since php is lazy when evaluating logical expressions, it is possible to use AND-operator instead of if-construct. See the following examples:

// example 1
if (foo())
{
  bar();
}

// example 2
foo() AND bar();

From what I understand, their results are the same: execute bar() if foo() evaluated to be true (or non-false, non-NULL, non-0).

Are there any differences?
In terms of execution time, example 2 may seem more efficient at a glace, but is it really the case once in machine code form?
In terms of semantics, I think they are different.

Any idea?

P.S. I have been searching for this but all I get is "Lesson 4: using AND operator with if statement"

[HalfaBee]

Example 1 is quicker than 2 and it is more obvious what is being done.

[bretticus]

Interesting, I've only done this in bash commands. I was curious so I wrote some code to test:

<?php
function dothis()
{
	return true;
}

function dothat()
{
	echo "hello world";
}


function microtime_float()
{
    list($usec, $sec) = explode(" ", microtime());
    return ((float)$usec + (float)$sec);
}

function dochained() {
	$time_start = microtime_float();
	dothis() and dothat();
	$time_end = microtime_float();
	$time = $time_end - $time_start;
	echo "\nDid chaining in $time seconds";
}

function dostarndard() {
	$time_start = microtime_float();
	if (dothis())
		dothat();	
	$time_end = microtime_float();
	$time = $time_end - $time_start;	
	echo "\nDid standard in $time seconds.";
}

dostarndard();
dochained();
?>

Next I ran this code several times and noted that the "chaining" command ran slower on average because I was calling dochained() first. When I put dostarndard() first, it showed the same average times (slower) as the other way around.

It appears to me that it makes no difference from my test.

Now, you might confuse some poor code maintainer someday. And of course, if your if statements need elses or complex nesting, than this manner may limit you somewhat.

[siriushoward]

bretticus, I tried with your code. whichever code run first would be slower

So I decided to loop dostandard() and dochained() a few more times. After the first call the two styles actually run at exactly the same speed. I did it on my own machine, turned off all other running applications.

And I also tried making dothis() return false and the results is slightly faster, as expected, but the two still running at exactly same speed.

More over: only the first call, dostandard() or dochained() ran first made no difference, takes longer and all the rest are the same.

From what I understand, If you run the same script function more than once, it is translated into machine code on the first call and the code is reused without translating thereafter which is why the first call takes longer. And the results shows that dostandard() and dochained() are reusing each others machine code! I suspect that they are exactly the same thing in php language!

I am only guessing tho. Anyone has enough knowledge to answer this?