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To: Mo McRoberts <mo@nevali.net>, php internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Simulating require_once within an extension
From: jochem@iamjochem.com (Jochem Maas)

I suspect you could implement the desired functionality
using http://php.net/manual/en/function.stream-wrapper-register.php

although I can't find any info on whether include/require
actually work with registered stream wrappers .. maybe one of the
devs could confirm/deny whether this is possible.

which would allow you to do something like this (assuming it is possible to do):

	require_once 'momcr://foo/script.php';

Mo McRoberts wrote:
> Hi list,
> 
> Apologies if I'm sending this to the wrong list; I couldn't see another
> which was more appropriate on the PHP Mailing Lists page.
> 
> I'm developing a PHP extension for which part of the functionality can
> be described in a nutshell as:
> 
> * at request start-up time, build a map of identifiers to path-names, read
>   from a configuration file;
>   
> * whilst a user script is being processed, a function provided by the
>   extension can be called to add, remove or modify items in the mapping;
>   
> * a user script can call a function, passing it an identifier in the map,
>   and the extension should simulate require_once being called with the
>   corresponding pathname (with some transformation applied).
>   
> For example, if the configuration file specified that 'foo' mapped to
> /www/common/foo, calling the above function with a parameter of 'foo'
> might simulate require_once('/www/common/foo/script.php') (where the
> transformation applied in this case is appending 'script.php' to the given
> pathname). A prototype implementation written in PHP itself works well enough,
> but obviously there are scoping issues with such an implementation (i.e.,
> any scripts included are included within the scope of the function, not the
> caller) which I want to avoid through the use of an extension.
> 
> Obviously, much of this is pretty trivial and straightforward. My problem is
> the actual simulation of require_once itself. As it's a language intrinsic,
> there's no simply-exposed API for performing the same action. Digging through
> the PHP sources, I've come across zend_execute_scripts(), which seems to
> fit the bill, although there's no documentation and very few examples of it
> being used outside of the PHP engine itself.
> 
> From skimming as many bits of the PHP sources that actually use
> zend_execute_scripts() that I could find, the code I've come up
> with isn't hugely dissimilar to this:
> 
> static int
> do_required(const char *filename TSRMLS_DC)
> {
> 	int r;
> 	zend_file_handle zh;
> 	
> 	if(SUCCESS != (r = zend_stream_open(filename, &zh TSRMLS_CC)))
> 	{
> 		return r;
> 	}
> 	if(NULL == zh.opened_path)
>    	{
> 		zh.opened_path = estrdup(filename);
> 	}
> 	if(zend_hash_add_empty_element(&EG(included_files), 
> 		zh.opened_path, strlen(zh.opened_path) + 1) == SUCCESS)
> 	{
> 		r = zend_execute_scripts(ZEND_REQUIRE_ONCE TSRMLS_CC, NULL, 1, &zh);
> 	}
> 	zend_stream_close(TSRMLS_CC);
> 	return r;
> }
> 
> Simple enough, right? Wrong.
> 
> I'm hoping at this point that somebody who knows the Zend internals pretty
> well will immediately spot which things I'm not initialising, saving/restoring,
> or happen to be double-freeing at this point, because I'm at a loss. My
> symptoms are this:
> 
> * If calls to this function are nested, and an inner call results in
>   zend_stream_open() failing, I get faults in zend_get_executed_lineno(),
>   suggesting corruption somewhere.
>   
> * If I save, reset and restore return_value_ptr_ptr, active_op_array, 
>   opline_ptr before doing anything, things seem better, but the Warning
>   message reported when the file can't be opened gives the error location
>   as [no active file] on line 0, which is less than ideal.
> 
> * If I only save/reset/restore around the call to zend_get_executed_lineno()
>   itself, things seem to work until I get as far as installing the extension
>   for my Apache 2.2 module build of PHP: at which point, as soon as there's
>   some nesting things start to go bad (errors reported or not). Removing the
>   final zend_stream_close() call stops Apache from dying, but I strongly
>   suspect that I'm just masking the problem rather than fixing it.
>   
> So, my questions are: what am I doing wrong, and is there a better way to
> accomplish the same thing? I considered evaluating a script instead of
> trying to simulate require_once itself, but that seemed incredibly kludgy.
> 
> Any help appreciated.
> 
> Thanks,
> 
> Mo.
>