Hi all,
I have a need for a package mechanism like that provided by TCL. We
write a
lot of code in reusable libraries and often encounter the situation in
which
an application uses a particular library but requires at least version X
or
greater.
The require(), require_once(), etc. functionality doesn't provide any
version
checking facility and I'm not aware of any other such mechanism built
into
PHP.
I played around with the following which kind of emulates the TCL
behaviour:
In each library I set a variable that contains that file's version
number
(automatically populated by CVS keyword expansion). I then replaced my
require() statements by a customised version which takes version number
arguments.
So, in my application script I have, for example:
require_once("package.inc");
package_require("libraryfile.inc", 1.5, 0);
...
And in package.inc I have:
function package_require($file, $minVersion, $maxVersion) {
require_once($file);
// Code to check if $file is within the specified bounds
}
The obvious (potential) problems with this approach are with respect to
scope. Most of the libraries I use contain function and class
definitions and
I'm not at all sure about the consequences of declaring these from
within
another function (package_require()). To my surprise, though, it seemed
to
work. No errors were generated and I could happily use the classes and
functions as usual. I'm a little nervous, though, about problems that
are not
immediately visible.
Secondly, there is the problem of global variables. Any variables set in
the
global scope in the library files are now in the local scope of the
package_require() function. I cannot put 'global' declarations for each
of
these as I would have to know about each and every one of them in
advance
which prevents it from being a general solution.
Does anyone else have some good ideas about this issue?
Are there any plans to implement this in PHP itself where it properly
belongs?
Thanks and regards,
Douw.
--
Douw Steyn - Visual Information Systems
Phone 27-21-4246290, Fax 27-21-4246208, email: [EMAIL PROTECTED]
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