How should boolean expressions be written in PHP?

Question

How should the following boolean expression be written in PHP:

$foo = "";
if($var==TRUE){
    $foo = "bar";
}

or

if($var==TRUE){
    $foo = "bar";
}else{
    $foo = "";
}

or

$foo = ($var==TRUE) ? "bar": "";

Answer 1

First off, true is not a constant, it's a token, so please don't uppercase it (I know some standards do that, but I think it confuses the meaning)...

Second, you don't need the redundant $var == true comparison inside the if. It's exactly the same as if ($var) { (For a double == comparison. An identical comparison === would need to be explicit).

Third, I prefer the pre-initialization. So:

$foo = '';
if ($var) {
    $foo = 'one status';
} else {
    $foo = 'another status';
}

If you don't need the else branch, just remove it. I prefer the pre-initialization since it forces you to initialize the variable, and it prevents cases where you forget to initialize it in one of the branches. Plus, it gives you a type hint when you go back to read the function later...

And for a simple branch like that, using the ternary syntax is fine. If there's more complex logic, I'd stay away though:

$foo = $var ? 'bar' : '';