hi,

AFAIK class constants are optimized for speed and therefore don't
support expressions; don't expect this to change any time soon ;-)

It would require to do a two passes compilation (or something along
this line) as you can define constants later in your script. They will
also be defined at runtime, not at buildtime. pecl's hidef may help
:).

Cheers,

Pierre

@pierrejoye | http://blog.thepimp.net | http://www.libgd.org

fqqdk wrote:

How about extending the usage of the 'final' keyword to support a java-like
syntax?

class Foo {
private static final $bar = 'ex' . 'pression';

In my book "final" in Java gets an award for sickest abuse of a keyword.
So no, I don't consider this an option. Simply use a class variable (or
define()) if you need to store some runtime calculated value.

"But <insert other language> can do this" alone is not sufficient as a
reason to bloat PHP IMHO.

• Chris

Hi,

2010/5/19 Tjerk Anne Meesters datibbaw@php.net

I wrote a small article that gives an idea of the speed differences:
http://shwup.blogspot.com/2010/04/about-constants.html

Unfortunately this doesn't tell, what you actually measured. And note
that as of 5.3 the "class constant" syntax can be used in the global
scope, too.

How about extending the usage of the 'final' keyword to support a java-like
syntax?

No. We have a const keyword. Rather somebody interested in this topic
might try to come up with a patch to at least allow "constant
expressions" this should serve most needs.

constant expressions might be stuff like DIR.'/foobar.php' or
CONST_A | CONST_B.

We already have two steps in the constant resolution for constructs like
these:

php > class A { const C = FOOBAR; }
php > define('FOOBAR', 42);
php > echo A::C;
42

See zval_update_constant_ex in zend_API.c as a starting point. While
such an approach would also require some parser work and some clever
idea where/how to store the expression to be evaluated etc.

johannes

On Wed, May 19, 2010 at 7:04 PM, Richard Quadling
rquadling@googlemail.com wrote:

On Wed, May 19, 2010 at 5:52 PM, Frederic Hardy
frederic.hardy@mageekbox.net wrote:

Hello !

AFAIK class constants are optimized for speed and therefore don't
support expressions; don't expect this to change any time soon ;-)

Is there any feature request about constant and expression ?
I would like to write something like that :

<?php

namespace foo\bar\directories {
   const tmp = DIR . '/tmp';
}

?>

So the best solution is something like <?php
define('foo\bar\directories\tmp', DIR . '/tmp'); ?>...
It 's strange that "define()" function can do something that the "const"
 keyword can't do, even if "const" keyword evaluation is done at compilation
time and "define()" evaluation is done at runtime.

That's why there's a cost penalty to using define().

I wrote a small article that gives an idea of the speed differences:
http://shwup.blogspot.com/2010/04/about-constants.html

Best regards,
Fred.

--

Frédéric Hardy : Architecte d'application/Admin. système/Ergonome
       Status : En recherche d'emploi

--

Tjerk

With regard to HiDef and the hidef.ini_path setting, and the comment
on [1] regarding "However, all this goodness comes with a drawback:
configuration settings are instance wide, which impacts all setups of
PHP that runs beyond a single web request (e.g. Apache module or
FastCGI).", could the ini entry be placed in a ...

[HOST=]

section in the ini file? [2]

If so, could this be the best solution?

The speed of hidef is accomplished by having only MINIT and MSHUTDOWN
handlers; it would be interesting to see how speed is affected by
moving some logic to the request init/shutdown; it should still have
the benefit of constants being defined at compile time.

Regards,

Richard.

[1] http://shwup.blogspot.com/2010/04/about-constants.html
[2] http://docs.php.net/manual/en/ini.sections.php

--

Richard Quadling
"Standing on the shoulders of some very clever giants!"
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