Request for Comments: Return type-hint

• Version: 1.0
• Date: 2010-07-28
• Author: Felipe Pena felipe@php.net
• Status: Under Discussion
• First Published at: http://wiki.php.net/rfc/typehint

The purpose of the RFC is to discuss about the return type hint utility on PHP.

• The old proposal (return and param type-hint) was introducing some keywords (the type names), with this new proposal there is no such BC.
• The new proposal has a better error message, identifying where the function/method was called.
• Added generic “numeric”, “scalar” types
• No needed strange syntax to solve parser conflicts

<?php
 
function scalar abc($x = NULL) {
	return $x;
}
 
var_dump(abc(1));  // int(1)
var_dump(abc(1.)); // float(1)
var_dump(abc());
/*
PHP Catchable fatal error:  The returned value must be of the type scalar,
called in ... on line 9 and returning in ... on line 4
*/

<?php
 
class Bar { }
 
class Foo extends Bar {
	public function Bar test($x) {
		return $x;
	}
}
 
$foo = new Foo;
$foo->test($foo);         // ok
$foo->test(new stdClass); // fail
/*
PHP Catchable fatal error:  The returned value should be instance of Bar,
called in ... on line 13 and returning in ... on line 7
*/

<?php
 
interface ITest {
	function string bar();
}
 
class Foo implements ITest {
	public function int bar() {		
	}
}
// PHP Fatal error:  Declaration of Foo::bar() must be compatible with that of ITest::bar() in ... on line 7

<?php
 
namespace foo {
class foo { }
class bar extends foo { }
}
 
namespace bar {
class bar {
	public function \foo\foo test() {
		return new \foo\bar;
	}
}
 
$bar = new bar;
$bar->test(); // ok
}

• See below some information that will be possible to be get using Reflection.

<?php
 
interface Test {
 
}
 
class foo implements Test {	
	function Test test() {
		return new foo;
	}
}
 
$func = new ReflectionMethod('foo::test');
var_dump($func->getReturnTypeHint());   // "Test"
var_dump($func->returnsObject());       // true

<?php
 
function scalar abc($x = NULL) {
	return $x;
}
 
$func = new ReflectionFunction('abc');
var_dump($func->getReturnTypeHint()); // scalar
var_dump($func->returnsScalar());     // true

<?php
 
class foo {
	function self bar() {
		return new foo;
	}	
}
 
$func = new ReflectionMethod('foo::bar');
var_dump($func->getReturnTypeHint()); // foo
var_dump($func->returnsObject());     // true

• Engine + Reflection: http://felipe.ath.cx/diff/returntypehint.diff
• Tests: http://felipe.ath.cx/diff/tests/return_typehint_tests.zip