PHP Coding Standards – Default Value Variable: Null vs Empty String vs False

I code to E_STRICT and nothing else.

Using empty and isset checks does not make your code ugly, it makes your code more verbose. In my mind what is the absolute worst thing that can happen from using them? I type a few more characters.

Verses the consequences of not using them, at the very least warnings.

In a weakly-typed language, type-casting exists to remove ambiguity in typed operations, when otherwise the compiler/interpreter would use order or other rules to make an assumption of which operation to use.

Normally I would say PHP follows this pattern, but of the cases I've checked, PHP has behaved counter-intuitively in each.

Here are those cases, using JavaScript as a comparison language.

String Concatentation

Obviously this is not a problem in PHP because there are separate string concatenation (.) and addition (+) operators.

var a = 5;
var b = "10"
var incorrect = a + b; // "510"
var correct = a + Number(b); // 15

String Comparison

Often in computer systems "5" is greater than "10" because it doesn't interpret it as a number. Not so in PHP, which, even if both are strings, realizes they are numbers and removes the need for a cast):

console.log("5" > "10" ? "true" : "false"); // true

echo "5" > "10" ? "true" : "false";  // false!

Function signature typing

PHP implements a bare-bones type-checking on function signatures, but unfortunately it's so flawed it's probably rarely usable.

I thought I might be doing something wrong, but a comment on the docs confirms that built-in types other than array cannot be used in PHP function signatures - though the error message is misleading.

function testprint(string $a) {
    echo $a;
}

$test = 5;
testprint((string)5); // "Catchable fatal error: Argument 1 passed to testprint()
                      //  must be an instance of string, string given" WTF?

And unlike any other language I know, even if you use a type it understands, null can no longer be passed to that argument (must be an instance of array, null given). How stupid.

Boolean interpretation

[Edit]: This one is new. I thought of another case, and again the logic is reversed from JavaScript.

console.log("0" ? "true" : "false"); // True, as expected. Non-empty string.

echo "0" ? "true" : "false"; // False! This one probably causes a lot of bugs.

So in conclusion, the only useful case I can think of is... (drumroll)

Type truncation

In other words, when you have a value of one type (say string) and you want to interpret it as another type (int) and you want to force it to become one of the valid set of values in that type:

$val = "test";
$val2 = "10";
$intval = (int)$val; // 0
$intval2 = (int)$val2; // 10
$boolval = (bool)$intval // false
$boolval2 = (bool)$intval2 // true
$props = (array)$myobject // associative array of $myobject's properties

I can't see what upcasting (to a type that encompasses more values) would really ever gain you.

So while I disagree with your proposed use of typing (you essentially are proposing static typing, but with the ambiguity that only if it was force-cast into a type would it throw an error — which would cause confusion), I think it's a good question, because apparently casting has very little purpose in PHP.