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.
_________________________________________________________________
Marc Liyanage http://www.entropy.ch
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