SammyK/php-function-header.md

## php-function-header.md

      
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              php-function-header.md
            
          
    I don't know enough about how programming languages work to even know what this is called. But when working on an event emitter, I thought it'd be cool if PHP would be able to support this:
class FooClass {
  function bam() { echo 'BAM!'; }
}

function foo(array $bar = []) {
  print_r($bar);
}

function foo(array $bar = [], $baz) {
  echo $baz . ' likes ' . $bar[0];
}

function foo(FooClass $bar) {
  $bar->bam();
}

$data = ['foo','bar']
foo($data);
// prints results from `print_r($data);`

foo($data, 'david');
// david likes foo

$fooObject = new FooClass();
foo($fooObject);
// BAM!
And I'm trying to figure out how it'd work with closures.
$myFunc = function (FooClass $foo) {
};
$myFunc = function (array $foo) {
};
This would make, for example, coding a Listener() super easy to write:
$listener = new Listener();

$listener->on(function (SuccessEvent $foo) {
  // . . .
});

$listener->on(function (ErrorEvent $foo) {
  // . . .
});

$listener->on(function (BarEvent $foo) {
  // . . .
});
Or is all this just a bad practice idea? Thoughts? :)