Re: [PHP] problem: creating global alias inside function
Hi,
Tuesday, July 29, 2003, 12:32:33 AM, you wrote:
MP> The following code illustrates a problem I've got with references (running
MP> on PHP 4.3.2). Can anyone explain it for me? Thanks in advance for any
MP> assistance!
MP> Martin
MP> $globalvariable = 0;
MP> $one = 1;
MP> //want to set up $globalvariable as a reference to $one
MP> setglobal($one);
MP> echo $globalvariable; //prints 0, not 1
MP> function setglobal(&$one)
MP> {
MP> global $globalvariable;
MP> $globalvariable =& $one;
MP> }
?>>
Now that I read what you really want :)
You can use a class to track a variable which may achieve what you
want like this:
class globalvariable {
var $gv = 0;
function globalvariable(&$var){
$this->gv =& $var;
}
}
$one = 1;
$g = new globalvariable($one);
echo 'global '.$g->gv.'';
$one = 2;
echo 'global '.$g->gv.'';
--
regards,
Tom
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Re: [PHP] problem: creating global alias inside function
Hi,
Tuesday, July 29, 2003, 12:32:33 AM, you wrote:
MP> The following code illustrates a problem I've got with references (running
MP> on PHP 4.3.2). Can anyone explain it for me? Thanks in advance for any
MP> assistance!
MP> Martin
MP> $globalvariable = 0;
MP> $one = 1;
MP> //want to set up $globalvariable as a reference to $one
MP> setglobal($one);
MP> echo $globalvariable; //prints 0, not 1
MP> function setglobal(&$one)
MP> {
MP> global $globalvariable;
MP> $globalvariable =& $one;
MP> }
?>>
You don't need the =& in the function as you are passing a reference
already. So you are setting $globalvariable to point to a reference
that is pointing to $one. You just need:
function setglobal(&$one)
{
global $globalvariable;
$globalvariable = $one;
}
--
regards,
Tom
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Re: [PHP] problem: creating global alias inside function
* Thus wrote Ford, Mike [LSS] ([EMAIL PROTECTED]):
> > -Original Message-
rints 0, not 1
> >
> > function setglobal(&$one)
> > {
> > global $globalvariable;
>
> PHP actually handles this by executing the equivalent of:
>
> $globalvariable = &$GLOBALS['globalvariable'];
>
> -- that is, it creates a $globalvariable *which is local to the function*
> and makes it be a reference to the global-scope variable of the same name.
>
> > $globalvariable =& $one;
Thus getting around the referenced global var, you can access
the global directly:
$GLOBALS['globalvariable'] = &$one;
Tested:
http://zirzow.dyndns.org/html/php/tests/misc/global_reference.php
Curt
--
"I used to think I was indecisive, but now I'm not so sure."
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RE: [PHP] problem: creating global alias inside function
> -Original Message-
> From: Martin Peck [mailto:[EMAIL PROTECTED]
> Sent: 28 July 2003 15:33
>
> The following code illustrates a problem I've got with
> references (running
> on PHP 4.3.2). Can anyone explain it for me? Thanks in
> advance for any
> assistance!
> Martin
>
>
> $globalvariable = 0;
> $one = 1;
>
> //want to set up $globalvariable as a reference to $one
> setglobal($one);
>
> echo $globalvariable; //prints 0, not 1
>
> function setglobal(&$one)
> {
> global $globalvariable;
PHP actually handles this by executing the equivalent of:
$globalvariable = &$GLOBALS['globalvariable'];
-- that is, it creates a $globalvariable *which is local to the function*
and makes it be a reference to the global-scope variable of the same name.
> $globalvariable =& $one;
This says to make the local $globalvariable be a reference to $one, *not* to
assign the value of $one to the variable referred to by $globalvariable --
so you've just overwritten the reference to the global $globalvariable with
a reference to $one! This means that you now have no way to refer to the
global-scope $globalvariable from within this function.
There are two key concepts here, which often seem to get overlooked:
(1) When you assign a reference to a variable which already contains a
reference, the action is to *replace* the existing reference with the new
one (*not* to assign the new reference through the existing reference).
(2) In a function, the global and static mechanisms are both handles by
defining variables local to the function which are *references* to the
appropriate location (thus, you *cannot* assign references to global or
static variables).
This is explained, albeit in a rather oblique way, on the manual page at
http://www.php.net/manual/en/language.variables.scope.php
Cheers!
Mike
-
Mike Ford, Electronic Information Services Adviser,
Learning Support Services, Learning & Information Services,
JG125, James Graham Building, Leeds Metropolitan University,
Beckett Park, LEEDS, LS6 3QS, United Kingdom
Email: [EMAIL PROTECTED]
Tel: +44 113 283 2600 extn 4730 Fax: +44 113 283 3211
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[PHP] problem: creating global alias inside function
The following code illustrates a problem I've got with references (running on PHP 4.3.2). Can anyone explain it for me? Thanks in advance for any assistance! Martin -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
