Problems with class definition

Anon

Just playing around with classes.. I'm getting incredibly frustrated with this....

filename blah.php

<?php
class TestClass {
var $server;
var $username;
var $password;
function setServer($arg) { $this->$server = $arg; }
function setUsername($arg) { $this->$username = $arg; }
function setPassword($arg) { $this->$password = $arg; }
function getServer() { return $this->$server; }
function getUsername() { return $this->$username; }
function getPassword() { return $this->$password; }
}

$DB = new TestClass();

$DB->setServer("localhost");
$DB->setUsername("username");
$DB->setPassword("password");

echo(" Server: "); echo($DB->getServer());
echo(" User: "); echo($DB->getUsername());
echo(" Password: "); echo($DB->getPassword());

has this output:

Server: password
User: password
Password: password

why the hell are all three variables getting the same value... oh, and if I do this:

$DB->setServer("localhost");
echo(" Server: "); echo($DB->getServer());
$DB->setUsername("username");
echo(" User: "); echo($DB->getUsername());
$DB->setPassword("password");
echo(" Password: "); echo($DB->getPassword());

it "looks" like it has worked properly (the correct values for the variables display)

is this a problem with my code? my setup? or what the hell!

Anon

Part of your problem is that when you reference variables which are internal to a class, you don't use the dollar sign ($).

For example, your references to:

$this->$server

should actually be:

$this->server

Also... you might find your classes a little less cumbersome if you forego the set and get methods and reference properties directly.

For example:

$DB->server = "localhost";

and

$server_name = $DB->server;

Hope this helps!
dp

Anon

Thanks mate.

It works now! damn I'm stupid

mithril

Another option is to use the constructor to set your class level vars. While PHP doesn't require a constructor method (and there are no destructors... though PEAR has a work about), I put them in all my classes for good form and setting vars. For example:

class TestClass {
 
    var $server;
    var $username;
    var $password;
 
    TestClass($strServer="",$strUsername="",$strPassword="")
    {
 
     $strServer != "" ? $this->server = $strServer : $this->server = ""; 
     $strUsername != "" ? $this->username = $strUsername : $this->username = ""; 
     $strPassword != "" ? $this->password = $strPassword : $this->password = ""; 
    }
 
}

The constructor accepts the server, username, and password arguments as optional and will set them if passed. The set methods can now be used to over-ride the defaults if need be. You'd call this class like so:

$DB = &new TestClass($server,$username,$password);

HTH.

Geoff A. Virgo

mithril

Damn...... my attempts at formatting arsed up🙂 Ignore the breaking space tags.

Geoff

Anon

Get rid of the $ off the variable name.

$entityObject->variablename

not

$entity->$variable

Object programming in PHP is also less strict than say Java. Using set and get methods for each and evry variable is not always needed.

Might like to use a default to

Function setServer($host="localhost",$user="root",$pass="pass"){

}

Means that the user can run the function using one or more of the parms and if non are used the defaults are set.

Anon

Geoff,

yeah I originally had a constructor setting up the variables (I cut the whole class down to post it here...). I still had the same problem, but it was because of the rogue $ sign in my variable references...

Its all good now, I'm coming from a asp/vbscript background and I'm, well, excited. I wrote a crappy ripoff of the ADO recordset object.. so now I can do this!:

$DB = new mDBConnection(L_DB_SERVER, L_DB_USERNAME, L_DB_PASSWORD, L_DB_CATALOG);
$DB->Open();
if ($DB->State()) {
    $RS = $DB->Execute("SELECT Headline, Username, Date FROM tblnews ORDER BY Date DESC LIMIT 10");
    while (!$RS->EOF()) {
        echo $RS->Field("Headline") . " - " . $RS->Field("Username") . " @ " . $RS->Field("Date") . "&lgt;br>";
        $RS->MoveNext();
    }
    $RS->Close();
}
$DB->Close();

So my foray into PHP classes has been a fun one, and not even frustrating except that first problem with referencing the variables incorrectly

Thanks for everyones help

mithril

Hi Sean,

Glad to hear it's working out for you🙂 Coupla things you might be interested in. First, the ampersand (sp?) operator. By default, all variable copies and objects in PHP are created by value not reference. However, using the amp. operator you can pass by reference and thereby reduce your memory usage to a minimum. Using your ADO class as an example, the syntax for class instanciations is as follows:

   $DB = &new mDBConnection(L_DB_SERVER, L_DB_USERNAME, L_DB_PASSWORD, L_DB_CATALOG);

The other is a class I came across on WeberDev some months ago. I've never used it since I personally find MS's DAO standard almost as cumbersome as ADO, but you might enjoy it considering your ASP/VBScript background. It's basically a MySQL wrapper which conforms to the MS DAO 3.5 spec's. The link is:

   http://www.weberdev.com/get_example.php3?count=3000

If this doesn't work (it's a framed site), simply go to www.weberdev.com and run a search on "DAO 3.5". You'll need to sign-up a WeberDev account (free) to view the source. HTH.

Cheers,

Geoff A. Virgo

Anon

Geoff,

ahh cool, yeah I was actually wondering how to pass variables by reference as opposed to value... otherwise I'm making unecessary copies of the objects.. in vbscript its all ByVal/ByRef... cool, thanks for the tip on that. 🙂

as far as the DAO wrapper.. I'll have a look at it, could be useful to learn from, but to be honest, just being able to loop back and forth through a result set is all I really needed...

That whole & thing is going to drop the memory usage a lot I'd say.. at a guess, I'm create 2 extra copies of the objects. (and it was using about 12mb of memory, for a big big recordset (about 1.5mb of data being pulled down)

Thanks again

Anon

Just had a look at that DAO code, hehe, its almost the same as mine 🙂

I wrote two objects.. mDBConnection, and mDBRecordset

the DB.Execute function returns a created recordset, otherwise you can create a seperate recordset yourself...

As far as functionality goes, they're almost identicial though

Thanks for the URL! 🙂