Why does PHP not have block-level scope? [closed]

Question

The PHP manual states that:

Any variable used inside a function is by default limited to the local function scope

I can't find any rationale for this architectural decision from the PHP designers. Why was PHP designed to only have local function-level scope, without block-level scope?

Answer 1

Because variables in PHP are not explicitly declared. Block scope for variables requires variables to be declared; otherwise, constructions like:

if ($condition) {
    $a = 1;
} else {
    $a = 2;
}
print $a;

wouldn't work correctly, because the "definition" of $a would be local to the branch where the variable was first assigned to.

The same principle applies to other languages which use implicit variable declarations, like Python.

Answer 2

I'm not sure what more we can add other than that's how Rasmus designed it. What was going through his mind at the time, I couldn't say.

You might be able to track down (or open up) some discussion about it on the PHP Internals mailing list, e.g. https://www.mail-archive.com/[email protected]/msg51630.html. As mentioned there, at this point it would be a huge BC-break, so it's unlikely to ever be implemented. But ultimately, it's a design decision like any other, and only the person who originally made it is going to be able to give you the "right" answer.