Posted by shimmyshack on 05/10/07 10:00

On May 10, 10:19 am, "liyan...@gmail.com" <liyan...@gmail.com> wrote:
> I recently worked on error handling and three related issues/questions
> came up.
>
> 1.) I am trying to trigger Apache ErrorDocument handlers by setting
> appropriate HTTP status codes in my PHP code, but I don't get the
> expected results.
>
> My PHP file:
>
> ----------------
> <?php
> header("HTTP/1.0 500 Internal Server Error");
> ----------------
>
> In my Apache configuration I have this:
>
> ----------------
> ErrorDocument 500 "test error 500 handler
> ----------------
>
> The status code is sent to the browser, but the ErrorDocument handler
> is never triggered, it looks like Apache passes the value on to the
> client, but does not interpret it.
>
> The last posting on this page suggests something to this effect:
>
> http://www.webmasterworld.com/apache/3205630.htm
>
> This surprises me, is that really how it works? In my Perl
> applications running under mod_perl, returning status 500 does *both*,
> send that status to the browser and make Apache interpret and act upon
> the value. What is mod_perl doing differently?
>
> I can actually have two separate status values, one that gets sent to
> the browser (Apache2::RequestRec::status()), and one that is returned
> to the Apache server (the handler() method's return value). Does
> something similar exist in PHP? Or do I really have to replicate the
> ErrorDocument functionality in my PHP code?
>
> 2.) In my tests with mod_perl just now I also realized that mod_perl
> will properly signal an error 500 condition to Apache if a Perl error
> such as a syntax error or an unhandled exception occurs. A configured
> ErrorDocument 500 handler will be triggered, as I would expect it to
> be.
>
> It seems that PHP does not signal an error 500 to Apache when PHP code
> fails. Wouldn't this be a useful addition for exactly this reason
> (ability to use Apache ErrorDocument).
>
> 3.) While playing around with set_error_handler(), I also saw that
> syntax errors are not trappable with a custom error handler. I use an
> autoloader that loads classes on demand, and if one of the class files
> loaded at run-time has a syntax error, my error handler is bypassed.
> Combined with the inability to trigger ErrorDocuments described above,
> doesn't this mean that it is absolutely impossible to hide such errors
> from users by replacing them with a "friendly" error page when using
> PHP?
>
> That would mean that I am not even able to emulate the ErrorDocument
> feature in PHP code.

well you /can/ do
sendErrorDocumentAndQuit($code)
{
$arrStatusCodes = array(
404=>'Page Not Found',
500=>'Custom Internal Server Error'
);
if( !in_array($code,array_keys($arrStatusCodes)) )
{
$code = 403;
}
header( 'HTTP/1.1 ' . $code . ' "' . $arrStatusCodes[$code] . '"' );
include( '/path/to/aliased/errordocs/'.$code.'.html' );
exit();
}


sendErrorDocumentAndQuit(404);

there's no 302, little overhead but of course emulating some of these
errors should only be done with care, 500 for instance. You are
"lying" about Apache's _real_ state, which is 200/304 if Apache is
really OK.

You're right though, there isn't the tight integration with Apache API
that Perl has.

Using mod_security - which of course is an apache module, you can trap
any response body string - such as errors, or <?php etc... that you
consider should never be sent to the user, so it should be possible to
spark off an action which might result in a standard error page.

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