Which is the better approach if I want my code to be efficient

Question

I didn't go to school when I started learning to code. I read books and browse the web. And this question really didn't appear in any of the books I read. And if I search it online I don't know what to search so I apologize in advance if this is obvious to you because it isn't to me.

Anyway is this approach better if I want my code to be efficient:

if($a == $b && $a <= $c && strlen($a) > 100 && functionA($a) && functionC($c)){
     //win
} else {
    //fail
}

OR

is this better:

if($a != $b){
    //fail
} elseif($a > $c) {
    //fail
} elseif(strlen($a) < 100){
    //fail
} elseif(!functionA($a)){
    //fail
} elseif(!functionC($c)){
    //fail
} else {
    //win
}

In javascript, I see compilers mash code up and eliminate all white space as possible and change variable names to a single letter (e.g. thisname to a) etc. In my understanding they do it so that the size of the javascript file is so small that when the page asks for it, loading time wouldn't be a problem.

But how about for php files? Which of the code above is better if I want my code to be efficient? why? AND Does the javascript scenario apply to php? Thanks

Answer 1

As has been noted in the comments, efficiency is the least of your concerns here, readability and thereby maintainability are more important. Typically you'd use a fail early approach to achieve this:

function myTest($a, $b, $c) {
    if ($a == $b) {
        return false;
    }
    if ($c < 10) {
        return false;
    }
    if (...) {
        return false;
    }
    ...
    return true;
}

Alternatively you may want to be throwing specific exceptions or return specific error codes instead of merely returning false to signal exactly what was wrong.

Answer 2

I'd say readability is most important factor, you won't win any speed anyway - compilers are quite smart.

if (passesRequirements($a, $c)) {
    //win
}

function passesRequirements($a, $b)
{
    return isNotEqual($a, $b)
        && isLargerThan($a, $b)
        && isShorterThan($a, 100);
}

function isShorterThan($str, $amount)
{
    return strlen($str) < $amount;
}

and so on.