====== Request for Comments: Short syntax for anonymous functions ======
  * Version: 1.0
  * Date: 2013-02-19
  * Author: Marcello Duarte <marcello.duarte@gmail.com>
  * Status: Draft
  * First Published at: https://wiki.php.net/rfc/short-syntax-for-anonymous-function
  * Other formats ..

===== Introduction =====

In some cases it is necessary that you have to pass an anonymous function to a function/method as a parameter. If your library receives uses an anonymous function, and alternatively nested anonymous functions, having the function keyword makes the code very long and unecessary unreadable. If you take a look at other languages (Ruby, Python, Groovy, Coffescript) there is a short syntax for closure using the language state block container. Maybe PHP should adopt this behaviour to make code more readable and maintainable.

===== Syntax =====

An anonymous function in php could be expressed by a typical statement block, surrounded by curly brackets.

<code php>
<?php
$sayHi = { echo "hi"; };
$sayHi(); // prints: hi

$sayHello = { $name => echo "hello, $name"; };
$sayHello("Chuck Norris"); // prints: hello, Chuck Norris

$sayHello = { $name, $mood => echo "hello, $name. It's $mood day!"; };
$sayHello("Chuck Norris", "wonderful"); // prints: hello, Chuck Norris. It's a wonderful day!
</code>

==== Passing an anonymous function to a function ====

The syntax allows for a cleaner way to pass a an anonymous function around.

<code php>
<?php

setFormattingStrategy({$string =>
    return trim(strtolower($string));
});

</code>

==== Adding variables to the function scope ====

<code php>
<?php

setFormattingStrategy({$string use $filter =>
    return $filter->trimedAndLowerCase($string));
});

</code>
===== What is common use cases in other language =====
==== Building domain specific languages ====

Some languages like Groovy and Ruby allows you to move the anonymous function outside of the list of arguments if it is the last argument of the function call, creating a interesting side effect.

<code php>
function describe($testedClass, callable $tests) {
    print ("$testedClass" . PHP_EOL);
    $tests();
}

function it($testName, callable $test) {
    print("    $testName" . PHP_EOL);
    $test();
}

// because the last argument is a callable we can now:

describe ("BankAccount") {
    it ("starts with a zero amount") {
        $amount = (new BankAccount())->getAmount();
        if ($amount !== 0) throw new Failure("Expected 0, got $amount");
    }
}
</code>

===== Pros and Cons =====

==== Pros ====
  * Good for framework development when more expressive callbacks are needed
  * Good for DSLs
  * Removes bloating, unnecessary syntax
  * Other web languages have similar syntax
  * Readable

==== Cons ====
  * Yet another alias
  * Would take distinctness from block statements
  * Not as searchable through search engines
  * Patch may be difficult to maintain in future

===== Changelog =====