Re: referencing an existing object

Torsten Roehr wrote:

"Justin Patrin" <papercrane@reversefold.com> wrote in message news:20040615162341.20005.qmail@pb1.pair.com...

Bernie wrote:

Howdy, I am writing a program that has a handful of classes. I would like to be able to get information from one object to the other. I have a couple of my classes extending others, but are there other ways to do

this?

For example: If I have a database class and a separate class that would like to execute an sql statement... class mydbclass { var $db; function mydbclass ($server,$username,$password,$database){

       $this->db=mysql_connect($server, $username, $password);
       mysql_select_db("$database",$db);

} function dosql($sql){

       $result = mysql_query($SQL,$db);

} } class myotherclass { function myotherclass(){

       $sql="select * from mytable";

       #now, how can I use $mydbclass->dosql($sql) to
       #execute this statement?

       #I want to be able to build a bunch of html with
       #the resulting records and it wouldn't make
       #sence to build all that in my db class

} } Thanks!

I would suggest something like this: class myotherclass {

    var $db

    function myotherclass(&$db){
        $this->db =& $db;

        $sql="select * from mytable";

        $this->db->dosql($sql);
    }

} $db = new mydbclass(); $other = new myotherclass($db); I would also suggest capitalizing the class names and using another DB abstraction layer (such as PEAR DB or MDB) but that's your option. ;-)

Good point Justin. You do not necessarily need a $db var in your data class - just use the passed $db object in your method: class myotherclass {

     var $db;

     function myotherclass(&$db) {

         $sql = 'select * from mytable';
         $db->dosql($sql);
     }

} Another way is to declare the $db variable global in your methods so that it is available without the need to pass it to *every* single method:

Global vars are generally a bad idea... It leads to spaghetti code and can end up giving you huge headaches if you're not very careful. Also, I am not saying that $db should be passed into every method. It should be passed into the constructor and assigned as a class variable (as my code above shows). Then, any method in the object can get to it.

class myotherclass {

     function myotherclass() {

         global $db;

         $sql="select * from mytable";
         $db->dosql($sql);
     }

} But this is a case of personal preference. Best regards, Torsten Roehr

-- paperCrane <Justin Patrin>