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Date: Wed, 1 Jul 2009 12:59:59 -0400
Subject: RFC: Type hinting revisited for PHP 5.3
From: ilia@prohost.org (Ilia Alshanetsky)

There has been quite a bit of discussion on this list, IRC, developer  
meetings, etc... about introduction of type hinting to PHP. Most  
people appear to think that this would be a good idea, but there is a  
reason why it is not in PHP already. The main source of conflict  
appears to be that in some cases typical type hinting is just too  
strict for PHP's typeless nature (most people expect that "1" == 1,  
while int type hint would definitely reject string "1").  Personally,  
I disagree with that opinion, but I can understand people who raise  
that issue. At work we've been using PHP 5.2 with type hinting for  
nearly 2 years now with great success, it makes code much easier to  
read and understand and the security benefit of type hinting is not to  
be under valued. In many cases type hinting can present a last line of  
defense against unexpected input for numeric fields, which are  
typically abused to do SQL injection.

I've taken a few hours this morning to port my 5.2 type hinting patch  
to 5.3. In recognition of a need for a more 'flexible' numeric type  
I've introduced (numeric) type hint that would allow bool/int/float  
data types as well as a string containing a numeric entity as  
identified by is_numeric_string(). For completion i've also added  
(scalar) data type that will allow any scalar data element.

The patch is available here: http://ia.gd/patch/type_hint_53.txt

It should be noted that this patch is fully compatible with opcode  
caches and and requires no changes on the part of an opcode cache such  
as APC to work.

My hope is that the latest changes will allow this to become a  
standard part of PHP.

Ilia Alshanetsky

P.S.

It should be noted that this is not the first idea for type hints,  
that credit goes to Hannes Magnusson who had posted a similar patch on  
the internals list back in 2006. Also, back in 2008 Felipe Pena wrote  
a type hinting patch for PHP that is available on wiki.php.net.