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Date: Thu, 12 Jul 2007 00:43:49 +0200
To: "PHP Developers Mailing List" <internals@lists.php.net>
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Subject: Apache handler with Multiple PHP versions
From: tijnema@gmail.com (Tijnema)

Hello developers,

The thread about dropping support for PHP4 gave me a new idea, having
multiple PHP versions to be loaded by the Apache2handler SAPI.

The idea:
I was thinking about something like the shebang(#!) line used in
bash/perl/python and even PHP scripts. But this time not for the
program to be executed, but for which PHP version to load. This could
be used like this:
<?php // PHP4 ?>
for PHP4, and so it could be
<?php // PHP5 ?> or <?php // PHP6 ?>
for resp. PHP5 or PHP6.
This way can scripts define which PHP version they require, as it is a
normal comment line, other PHP version can simply ignore the line.

The implementation:
The Apache2handler SAPI should be loaded first, and read the very
first line of the PHP script to determine if a version is specified
there. If not, the handler needs to load its default PHP version. If
it is specified, it should try to load that version, and if it
couldn't find or load that version, fall back to the default version
and issue a warning.

What needs to change:
Currently, PHP is one big module for Apache, which will load a full
PHP version at once. For this, we require a very small handler, that
will use dlopen() to load the appropriate version and continue with
the execution of the PHP script.
Some kind of mini parser is also required to read the very first line
of a PHP script, because that needs to be done before any PHP version
is loaded. And maybe also a parser for the php.ini file, as php.ini
needs an extra option for the default PHP version to be loaded, and
one or more settings for configuring the different PHP versions and
their path to the library.

Some extra ideas, not sure if they need to be implemented:
* Support for sub versions of PHP, like this:
<?php // PHP4.3 ?>
<?php // PHP5.2.1 ?>
* Support for multiple possible PHP versions, like this:
<?php // PHP4 || PHP5 ?>
Where the first one is the preferred one, which can also be combined
with the first one of course, like this:
<?php // PHP5.2.1 || PHP5.2.0 || PHP 4.3 ?>
* Support for <, > and && signs in the version, like this:
<?php // PHP > 5.2 && PHP < 5.3 ?>
So that any PHP version between 5.2 and 5.3 fits, but that 5.2 is the
preferred one, if 5.3 should be the preferred one, it should be
written like this:
<?php // PHP < 5.3 && PHP > 5.2 ?>
* Support for this in other handlers, like FastCGI, ISAPI, etc.


It seems to be the perfect solution for shared hosting providers to
me, as it will allow the user to select which PHP version he wants to
use, and shared hosts can just install all three versions of PHP and
use the one they need for their admin panels etc. (One of the reasons
against upgrading to PHP5), and users can use another version.
I don't know too much about PHP core, and nearly nothing about the
apache2handler, so if it's not possible, please excuse me for wasting
your time.
But, if it is possible, I will definitely go deeper inside the core
and SAPI code to get it working.

Now, the reason I'm sending this to the list is that I need to know if
*) it is possible?
*) it is not yet done
*) it is wanted
*) it will have any negative effect on something?

I'd like to hear all your comments and objections on this, and of
course, if you have any question, feel free to ask.

Regards,

Tijnema