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Posted by Julien Biezemans on 06/25/07 15:11
Hi!
Here is another post concerning stream wrappers. I'm trying to implement
a urn: scheme stream wrapper but this does not seem possible with PHP.
Why? Because PHP analyzes URI with the following syntax:
scheme "://" target
Where _scheme_ is what they incorrectly call a "protocol" in the
documentation and _target_ the actual target of the URI.
When dealing with things like http://www..., ftp://ftp..., everything is ok.
But how are we supposed to support things like mailto:user@domain.com,
urn:xmpp:..., h323:host... and other schemes that are NOT followed by
"://" but only ":"?
If you try to register the mailto "protocol" (which is, again, not the
correct term), you will do:
stream_wrapper_register('mailto', 'MyMailToClass');
But this wrapper class will not be used at all by PHP if you try this:
fopen('mailto:user@domain.com', 'w');
Instead you will have to write:
fopen('mailto://user@domain.com', 'w');
Which is wrong (see http://www.rfc-editor.org/rfc/rfc2368.txt).
PHP consider that 'mailto:user@domain.com' falls into the default
(file://) scheme as it does not find the "://" string after the
so-called "protocol".
We may intercept URI's not containing those "://" characters with a
custom file:// stream wrapper. When the wrapper is called by PHP and the
"path" starts with a recognized scheme like "mailto:", it may delegate
the work to the actual mailto: wrapper. But this is just a workaround as
it is supposed to handle resources on the local filesystem only.
I understand that this behavior is probably caused by
fopen('some:file.dat'); being mostly used to open a file that has a
column character in its name and located in the current working
directory (: character is not allowed in file names on windows, I
guess). It simply demonstrates once again a problem that may arise with
the default implicit file:// scheme in URI's.
Anyway, I'm still posting to read your thoughts on this. Maybe someone
will see another solution than the workaround I explained above.
Thank you!
Julien.
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