[PHP] Variable (Class instantiation) collision

[Brian Smither]

I am running into a variable collision. The project I'm developing is NOT 
guaranteed to be operating on PHP5. Any solution I find should (hopefully) be 
able to run on PHP4 (yes, I know PHP4 is deprecated).

I am building a bridge between two third-party applications. Both instantiate 
their respective database class assigning it to $db and I cannot change that.

So, I am interested in solutions to this.

I found a reference to a Packager class and will be looking at it shortly.



--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php

Re: [PHP] Variable (Class instantiation) collision

[chris h]

Just to clarify, both packages are instantiating and calling their
respective database classes from the $db var, which is in the global scope.
Is this correct?

This is why I hate the global scope, I hate it, I hate it!

On Tue, Oct 5, 2010 at 3:47 PM, Brian Smither bhsmit...@gmail.com wrote:

 I am running into a variable collision. The project I'm developing is NOT
 guaranteed to be operating on PHP5. Any solution I find should (hopefully)
 be able to run on PHP4 (yes, I know PHP4 is deprecated).

 I am building a bridge between two third-party applications. Both
 instantiate their respective database class assigning it to $db and I cannot
 change that.

 So, I am interested in solutions to this.

 I found a reference to a Packager class and will be looking at it shortly.



 --
 PHP General Mailing List (http://www.php.net/)
 To unsubscribe, visit: http://www.php.net/unsub.php

Re: [PHP] Variable (Class instantiation) collision

[Brian Smither]

Just to clarify, both packages are instantiating and calling their
respective classes from the $db var, which is in the global scope.
Is this correct?

I would say yes to the way you are asking. Take the following two applications. 
The four respective statements are in each their respective script.

Application A:
?php
class foo {}
$db = new foo();
$outA = barA();
function barA() { global $db; include(Application B); }
?

Application B:
?php
class bar {}
$db = new bar();
$outB = barB();
function barB() { global $db; }
?

The bridge project is operating in A and include()'ing the script that is B (as 
I have not found an API for B). $db in B is colliding with $db in A.



--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php

Re: [PHP] Variable (Class instantiation) collision

[chris h]

Short of refactoring ApplicationB, can you set it up as a SOAP/REST service
that AppA calls?


On Tue, Oct 5, 2010 at 5:02 PM, Brian Smither bhsmit...@gmail.com wrote:


 Just to clarify, both packages are instantiating and calling their
 respective classes from the $db var, which is in the global scope.
 Is this correct?

 I would say yes to the way you are asking. Take the following two
 applications. The four respective statements are in each their respective
 script.

 Application A:
 ?php
 class foo {}
 $db = new foo();
 $outA = barA();
 function barA() { global $db; include(Application B); }
 ?

 Application B:
 ?php
 class bar {}
 $db = new bar();
 $outB = barB();
 function barB() { global $db; }
 ?

 The bridge project is operating in A and include()'ing the script that is B
 (as I have not found an API for B). $db in B is colliding with $db in A.



 --
 PHP General Mailing List (http://www.php.net/)
 To unsubscribe, visit: http://www.php.net/unsub.php

Re: [PHP] Variable (Class instantiation) collision

[David Harkness]

If you have total control over application A which contains the bridge code,
the easiest is to change it to use a different global variable, $dbA. This
must not be doable or you wouldn't have asked.

If you have control over the bridge code, and it alone calls A and B, then
you could swap the $db variables between calls:

$db = null;
$dbA = null;
$dbB = null;

function copyPersons() {
useA();
$persons = loadPersonsFromA();
useB();
savePersonsInB($persons);
}

function connect() {
global $db, $dbA, $dbB;
connectToA();
$dbA = $db;
unset($db);
connectToB();
$dbB = $db;
unset($db);
}

function useA() {
global $db, $dbA;
$db = $dbA;
}

function useB() {
global $db, $dbB;
$db = $dbB;
}

This is the simplest implementation. You could get trickier by tracking
which system is in use and only swapping them as-needed, writing a facade
around the APIs to A and B. It's ugly, but it works.

David