Passing a Class

Cogen

First of all let me just say I have never used a class in PHP!

I was wondering how I would pass a class between pages? Is this possible? I'm creating an inventory module for an administration site, and I would like to create an Items class to hold such things as itemid, price, tax, etc. Just for testing purposes, I have created a couple pages to see if I can pass an object between them. I am having no luck. Please help if you can, it would be appreciated. Here is the method I have been trying. (It's just a skeleton right now, but if I can get this working then I can elaborate on it)

CLASS..

class InventoryItem {
	var $memID;
	var $memBasePrice;

function InventoryItem($ID) {
	$this->memID = $ID;
}

function get_ID() {
	return $this->memID;
}

function get_BasePrice() {
	return $this->memBasePrice;
}

function set_BasePrice($BasePrice) {
	$this->memBasePrice = $BasePrice;
}
}

//PAGE1..

$objItem = new InventoryItem(99);
echo "My item id is =".$objItem->get_ID(); //works fine

//these lines are straight html..
<form action="index.php?page=page2" method="post">
<input type="hidden" name="myclass" value="<?= $objItem?>">
<input type="submit" name="submit" value="Submit">
</form>

//PAGE2.. (doesn't work)

$myobj = $_REQUEST["myclass"];
echo "My passed item id is =".$myobj->get_ID();

PyroX

Look into using serailize and unserialize.

ednark

basically three methods...

PyroX's suggestion serialize the object: this makes it into a string which can be passed between pages. but thats unnecesarry, php already has a mechanism that preserves arbitrary data between page calls the $_SESSION array, anything places in there will exist for that same user between page calls. php sets a cookie or passes a sesssion id along within each link which allows the server to identify each individual user.

you can place the entire object into a $SESSION and then it will exist between page calls. $SESSION['myobj'] = $obj_i_just_made

you can write out the objects values into an html form and the have the user change values/submit form. then the page that accepts the form can use the values to repoplate a new object of the same type

if the object lives in a database, you can give it a unique id, pass that unique id between pages, and then pull it out of the databse again on the recieving page.

Cogen

Thanks for the help guys 🙂. I have it working using sessions now.

ednark ... Just out of curiosity, is it hard putting an object in a database? What I plan to do is also create an Invoice and Receipt classes, and each of them will have an array of Items classes containing the items they have. If I can then put the invoice/receipt class in a database that would be amazing. I know this might be tricky so I can do my own research, I just thought you might know where I can start. :p

PyroX

ednark is of course 100% accurate in his post.

I am used to putting objects into a db or tmp session file, so I always have used serialize(), I may not be doing that in the most efficient way either.

Cogen

thanks for the post anyway PyroX. As I stated above, I would like to insert my classes into a database also (for a history of invoices/receipts), so I might have to use serialize yet!
🙂

PyroX

Its not too tricky to put it into the database, the way I do this looks something like this:

$static = serialize($object);

mysql_query("insert into tablename (objects) VALUES ('$static')",$dbref);

And then when you pull it back out of the database:

$object = unserialize($static);

There are examples here:
http://www.zend.com/manual/function.serialize.php
http://www.zend.com/manual/function.unserialize.php

ednark

listen to pyrox hes right on the money with object serialization int databases and cookies.

if you want to put the obj into a databse you simple serialize it (makes simple ascii string) and store that int the text field of your table..

however that defeats the purpose of a relational database, which is to preserver and allow searching dependant on the properties.. if you mush them all up into one string it doesn't give you that capability

now you may not need to search on any individual fields of the object.. in that case serializing is fine.

another alternative is to create one table for an object.. and give each of its vars a column.. and then have the object upon creation pull from the database a row that represents itself... an example of this is DB_DataObject from pear.php.net

also to take into consideration when serializing is class changes.. if you make any changes to the class data you serialzed.. like updated it somehow.. then any things you serialized in the past won't unserialize correctly... so you will have to re-pull out all object in the database and change them into the new format... kinda messy