RFC for conditional break, continue, & return statements

[ralphschindler]

RFC at: https://wiki.php.net/rfc/conditional_break_continue_return

First pass at first class syntactic support for "guard clauses". More technically, a return if.

Example:

function divide($dividend, $divisor = null) {

    return if ($divisor === null);
    
    return if ($divisor == 0): 0;
    
    return $dividend / $divisor;
}

var_dump(divide(10)); // null
var_dump(divide(10, 0)); // 0
var_dump(divide(10, 5)); // 2

https://stackoverflow.com/questions/5436034/is-there-a-ruby-one-line-return-if-x
https://engineering.helpscout.com/reducing-complexity-with-guard-clauses-in-php-and-javascript-74600fd865c7
https://guidelines.spatie.be/code-style/laravel-php#avoid-else (avoid else)

[carusogabriel]

With this grammar, if without () does not work, e.g.:

<?php

function divide($dividend, $divisor = null): ?int {
    return if $divisor === null; // return null

    return if $divisor === 0 : 0; // explicit return value

    return $dividend / $divisor;
}

Is that expected?

[ralphschindler]

yes, as currently it is re-using as much syntax that already is known and exists in php. open to discussion though.

[nikic]

    return if ($divisor == 0): 0;

This bit of syntax looks very peculiar. Why is this not return 0 if ($divisor == 0);?

[ralphschindler]

I think it is important to communicate the conditionalness of the return early on, as well as what the conditional is, regardless of the length of the response expression.

Since my reasoning requires visuals... :D

edit: also, the: expression for the optional return expression at the end of the full clause has some symmetry with the return type hints in the method signature.

(might have to click to open to see full image)

I will bring to list, more people may have an opinion on order. FWIW, this order was one of my harder decisions up front, I see both ways.

[iluuu1994]

I think it is important to communicate the conditionalness of the return early on

Then why not just if (condition) return;? It's also the exact same length. I know other languages do this too but I personally never saw the need for it (but that's one opinion).

[ralphschindler]

Then why not just if (condition) return;? It's also the exact same length. I know other languages do this too but I personally never saw the need for it (but that's one opinion).

Good points, I think to further clarify my position, this is the priority, order, and intent I wish the statements to communicate:

1. yes, this line is a return (evident by return being left-most/first on a line)
2. yes, this return is conditional (evident by the if immediately following the return)
3. then, the condition itself
4. optionally, some return value

Even if these statements span multiple lines, this priority and order remains intact to a large degree.

As mentioned in the https://externals.io/message/110107 thread, I am away this is syntactic sugar to some degree, but I feel as proposed, it adds a tremendous amount of value.

[zmitic]

Sorry to break in but can this RFC be enhanced with throw? Example:

throw if (!$user = $this->getUser()) : new AccessDeniedException();

If so, it could be expanded with positive if comparison in future:

throw unless ($user = $this->getUser()) : new AccessDeniedException();

One-liners like above would be really nice and readable.

[iluuu1994]

throw unless ($user = $this->getUser()) : new AccessDeniedException();

In PHP 8 you can do this:

$user = $this->getUser() ?? throw new AccessDeniedException();

Which is shorter and way less complex.

[derickr]

Please don't forget the newline at the end here :-)

[guss77]

Why not just implement full postfix conditions, like in Perl and Ruby? This will allow (almost) the syntax as requested by this RFC but will be a lot more useful:

"fail-fast":

return null if (!$input);

populate values quickly:

$error = "missing home" if (!$home);

Throw errors (like @zmitic) asked:

throw new Exception() if (!$valid);

And if the "guard RFC" will be changed to unless (again, like Perl and Ruby), you'd get even simpler syntax for free:

return null unless($input);

[iluuu1994]

@ralphschindler Are you planning on pursuing this RFC?

[iluuu1994]

Closing since there was no response.