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Organization: Parliament Hill Computers Ltd
User-Agent: Mutt/1.5.20 (2009-12-10)
Subject: Re: [PHP-DEV] PHP and case-sensitivity inconsistency in PHP 6
From: addw@phcomp.co.uk (Alain Williams)

On Sun, Jan 26, 2014 at 03:36:08PM -0800, Stas Malyshev wrote:
> Hi!
> 
> > So essentially, I would like to see case sensitivity at call time
> > (called name must match declaration), but case insensitivity at
> > declaration time (when checking whether a symbol has already been
> > declared):
> 
> What would function_exists('Foo') return when foo() is defined?
> 
> If false, then this code:
> 
> if (!function_exists('Foo')) {
>   function Foo() { ... }
> }
> 
> would not work. If true, then this code:
> 
> if(function_exists('Foo')) {
>   Foo();
> }
> 
> would not work. Both are working fine now and there's no real reason why
> shouldn't they keep working.
> 
> Additionally, making the engine case-sensitive would simplify some areas
> of function/class handling. But making it inconsistently partially
> case-sensitive would instead complicate it, as we now would have to make
> additional checks against original name before calling.
> 
> My opinion is if we go case-sensitive, it must be full case sensitivity,
> no exceptions.

+1

We need to think about:

* there are a few special values that are currently case insenitive, eg: NULL, TRUE.
  I would suggest that they only be recognised in upper case, eg: null would be
  invalid. This fits with the meme of constant names being in upper case.

* transition, there must be a lot of code that has (accidental) case
inconsistencies in function/variable/...  names.  If PHP were not a dynamic
language (eg C) then this change would be caught at compile time. In PHP a case
inconsistency is only found when the code is executed. Programs can contain
blocks of code that are rarely executed - think: rare error recovery.

Something that would help with transition is the option to force variables to
be declared. If a variable is then used without being declared an error is raised.

We currently have the problem as illustrated below:

    $foo = 'bar';
    echo "foo=$f00";

With case insensitivity this problem will become worse.

What I propose is something like perl's 'use strict'. This causes a compilation
error if a variable is used that has not been defined. This pragma applies only
for the compilation module that it is in; ie it does not apply to 'include'd
files and so can be done on a module by module basis.

The way that I suggest that we do this is by using the existing keyword 'var'. Eg:

    var $foo = 'bar';
or
    var $foo;

If 'var' is seen in a module, then use of any variables below MUST be for
variables that have been declared.

OK: that is the general idea, details need working on.


Note that the use of 'var' to declare variables is OPTIONAL, only use it if you
want to.

-- 
Alain Williams
Linux/GNU Consultant - Mail systems, Web sites, Networking, Programmer, IT Lecturer.
+44 (0) 787 668 0256  http://www.phcomp.co.uk/
Parliament Hill Computers Ltd. Registration Information: http://www.phcomp.co.uk/contact.php
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