[wp-hackers] register_activation_hook() problem

[Adam Taylor]

Cheers for the extremely thorough heads-up on globals - I shall go read that
link.

Thanks,
Adam

On Tue, Jul 28, 2009 at 5:21 PM, Chris Jean <gaarai at gaarai.com> wrote:

> In that code, I did not see a redefinition. However, if you have other
> plugins, theme mods, etc that define that function, you will still have
> problems. Keep in mind that redefinition isn't limited to a file, it
> applies to all code that runs.
>
> Looking at your code, it is clear that you still need to learn how
> globals work. The code fatally failed because you didn't have "global
> $wpdb" inside the createDatabaseTables function. Also, thumbs_install,
> thumbs_init, and process_vote will not use the $thumbs global thumbs var
> as you want since the global var is not localized to the functions.
>
> Scope is really odd in PHP; frankly, I don't like how it works. So,
> forget everything you knew about scope in other languages and learn how
> PHP does it.
>
> When you create a function, you create a new scope completely-unique to
> that function. Nothing exists to that function except what is passed to
> it as an argument or what is created inside of it. Even though a
> variable may be global, it does not exist inside any function.
>
> The way you bring a global into the function is to use the global
> keyword to bring the global variable into the function's scope.
>
> For example, doing the following will not work:
>
>    global $var;
>    $var = "Hello!\n";
>    test();
>
>    function test() {
>        echo $var;
>    }
>
> The function test creates a new empty variable called $var and echoes
> it's value rather than using the global. Running the code will result in
> a warning: "PHP Notice:  Undefined variable: var in ..."
>
> This is the right way to do it:
>
>    global $var;
>    $var = "Hello!\n";
>    test();
>
>    function test() {
>        global $var;
>        echo $var;
>    }
>
> You can read more on globals here: http://bit.ly/18fGqF
>
> With all this said, I recommend that you avoid globals if you can.
> Passing variables as arguments or storing them in objects is a
> less-confusing and less bug-prone way of doing things.
>
> Chris Jean
> http://gaarai.com/
> http://wp-roadmap.com/
> http://dnsyogi.com/
>
>
>
> Adam Taylor wrote:
> > On Tue, Jul 28, 2009 at 4:54 PM, Chris Jean <gaarai at gaarai.com> wrote:
> >
> >
> >> Your error is caused by the fact that the thumbs_install function is
> >> being redeclared, not by your use of the global declaration. You can
> >> only define a function once, attempting to do so again will result in an
> >> error.
> >>
> >>
> >
> > I'm pretty sure I haven't defined the function more than once.. the whole
> > code is here:
> >
> > http://pastebin.com/m1feb2d16
> >
> > If that helps anyone help me..
> > _______________________________________________
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> > wp-hackers at lists.automattic.com
> > http://lists.automattic.com/mailman/listinfo/wp-hackers
> >
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