Re: [PHP] uh oh, I defined a resoruce

On Jan 10, 2008 2:02 PM, Philip Thompson <philthathril@xxxxxxxxx> wrote:
On Jan 10, 2008, at 12:48 PM, Eric Butera wrote:

On Jan 10, 2008 1:33 PM, <reese@xxxxxxxxxxxxxxxx> wrote:
I have been using define to create a constant for the link resource
returned by mysql
pconnect like so:

$PL = @mysql_pconnect("localhost", $DBUser, $DBPass);
define("SITE_DB",$PL);


Later I use the constant to select my databases.

mysql_select_db($SrcdbID ,SITE_DB);

This code seems to be working as I expected and I have many
thousands of llines of code
done over several years using this construct.

But, I happened to be reading the php doco today and noticed that
you are not supposed to
use define for resources, so question is, is what I am doing safe
or am I going to run into
problems and if so what is the best way to globally pass resources
to multiple classes and
functions, command line scripts etc?


Cheers
Charlie Reese


Hi Charlie!

Well a CONSTANT is a value that doesn't change. I don't think that
makes sense for a DB connection. The connection command returns a
resource that could be different on each request depending on if
you've worked on different resources.

You could just do this:
$GLOBALS['SITE_DB'] = @mysql_pconnect("localhost", $DBUser, $DBPass);

Then inside your function reference it like this:
mysql_query($sql, $GLOBALS['SITE_DB']);

This would be an easy mass find/replace that you could do. Global
variables are evil though.

I personally use the registry pattern to hold an instance of the
database connection that can be lazy loaded whenever I need it. Then
inside of my gateway objects I pass that instance in the constructor
so they only have to know how to work with its interface. If you're
okay with using object that might be a nice road to travel. You could
also use the singleton pattern but I would advise against that because
what if you wanted 2 instances for different databases? I've never
ran across this myself but you never know. Plus it makes unit testing
a little tricky since you can't mock it as easily.

Hopefully something in all this will help you to an answer.


I don't agree that "Global variables are evil." If you have a valid
purpose for defining a global variable, then go with it. The usual
argument is that it could accidentally be changed elsewhere (and there
are several more). However, defining a variable that you KNOW you're
going to use only for a database connection, IMO, is perfectly fine.

$GLOBALS['SITE_DB'] = @mysql_pconnect("localhost", $DBUser, $DBPass);

If you accidently change $GLOBALS['SITE_DB'] elsewhere, then I think
you have some bigger issues at hand. =P HTH.

~Philip

"Personally, most of my web applications do not have to factor 13.7
billion years of space drift in to the calculations, so PHP's rand
function has been great for me..." ~S. Johnson

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Depending on what project I'm working on sometimes I use specific
globals on our older procedural code because:

1) It is our code
2) It does not use outside code
3) I'm the only developer working on it
4) It is very simplistic

By specific globals I mean that I have a "namespaced" entry such as
$GLOBALS['ericonly']['db'] and put things inside of ericonly. I
basically only use this for database connections and a few other very
specific things.

Aside from that I'm not going to argue the merits of globals. Someone
else can do that as I've made up my mind and so have you. :)

But just to prove that I'm right
http://www.google.com/search?hl=en&q=global+variables+are+evil&btnG=Search
:D
.

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