What I don't understand is what the issue with that is?
You can already build up a named array and splat it into a function call to pass by name. It's a really neat trick. It doesn't need a dedicated function.
About a month ago, I went through all of TYPO3 and removed all remaining call_user_func_array() calls in favor of just $function(...$args), because it does the same thing and is faster, and easier to read. Named arguments already work exactly that way, too.
I don't see an advantage to adding a function that does what you can already do with less syntax:
$args['foo'] = 5;
$args['beep'] = get_value_from_db();
$args['narf'] = 'poink';
$callable(...$args);
That works today in 8.0. We're good.
The proposal focuses on the onus put on the author of the closure/function, not the caller.
If your $callable is only interested in $foo enforced as an int and $narf enforced as a string, what does the signature and body of the subscribing $callable look like in this case?
I am proposing that if a system is providing all of this for any registered callables:
$args['foo'] = 5;
$args['beep'] = get_value_from_db();
$args['narf'] = 'poink';
$args['boop'] = $boopObject;
$args['isNoomable'] = false;
But are only interested in value for 'foo' and 'narf', they can still get type hinting/checking/enforcement and the benefits of named mapping.
Let's assume the following which has a little bit of context:
// developer/consumer code
$library = (new SomeLibrary)
$library->registerCallback(function ($foo, $narf) {});
$library->call();
// some 3rd party library with a callback system in place
class SomeLibrary {
public function registerCallback(callable $callback) {
$this->callback = $callback;
}
public function call() {
if (!$this->callback) {
return;
}
$args = [];
$args['foo'] = 5;
$args['beep'] = 'value from db';
$args['narf'] = 'poink';
$args['boop'] = new StdClass;
$args['isNoomable'] = false;
($this->callback)(...$args);
}
}
This will fail with message:
PHP Fatal error: Uncaught Error: Unknown named parameter $beep in ...
Currently, the consumer/developer would have to write:
$library->registerCallback(function (...$args) {
$foo = $args['foo'];
$narf = $args['narf'];
// ...
});
// or
$library->registerCallback(function ($foo, $beep, $narf, $boop, $isNoomable) {
// do something with foo or narf
});
Additionally, the library/framework is now precluded from adding new parameters since any consuming callables would also have to introduce these new parameters as it could be considered a BC break.
The more I think about it though, the more sensible this would be as it allows the callback provider to opt into named parameter mapping destructuring:
$library->registerCallback(function (...[string $foo, string $narf]) {
// do something with $foo and $narf
});
-ralph