multiple feild primary key

Hi
As most here I am working on stuff. This is my first app and database from the ground up. Now to the point
I have created the following tables to manage an art portfolio. For each piece there will be one "port_inventory" entry, there can be multiple "port_images" and "port_text" entries that relate to "port_inventory" (tables at end of post). When creating the tables I set invID in "port_inventory" as primary, in the other two tables I used invID and txtID or imgID as the primary key. In the tables images and text I did not set the primary key's to auto_increment, invID if it autos it will be different the the inv it is supposed to reference, the other two I did not so I could now how many instances were for each invID ( I was hoping for a primary key result like invID 1 txtID 1, invID 1 txtId 2 and so on)
I one problem and another question.
Question, is the way I have this a good idea? Or is there a better option for what I have done.
The problem, I can add data to any of the tables, I am having problems when it comes to UPDATE of the fields here is the code I am using

I dont know how to choose multipe $id's, when I run this as I have it, it returns the form but with empty fields, and if I change the data, nothing is updated.

I am sure there are many obvious errors, but I am dense.
Many thanks.

Try:

$sql = "UPDATE port_images SET full='$full',large='$large',medium='$medium', small='$small',invID='$invID' WHERE imgID='$id'"; // added ' to imgID=$id

Use

$result = mysql_query($query) or die(mysql_error());

to execute.

As for your other concerns, I really have no idea what you are talking about. If you have a concern about your design stragtegy there is really no need to list a fleet of strangely-named variables, neglect to describe their relevance, and moreover use just a single paragraph for that enhanced readability everyone loves.

Just outline the idea and specify what you think could be improved. Do you have any design diagrams?

Sorry for the confusing post.

Here is a better table diagram.
port_inventory is the main table, the field invID is auto_increment, then used for the following table. The primary keys for the text and image tables is a combination of the id from that table and the invID. I did not set the id fields for text an image tables to autoincrement.
Is this a sound design strategy, or should I have a field that is auto_increment? Or are there other problems that I should address at this stage.


table port_inventory PRIMARY KEY (invID)
--------------------------------------------------------------------------
| authID | invID | artist | title | medium | year | date | sizeH | sizeW |
|------------------------------------------------------------------------
| 1 | 1 | artist name | title a | oil on canvas | 2001 | 01-01-2003 | 18 | 24 |
| 1 | 2 | artist name | title b | oil on canvas | 1998 | 01-01-2003 | 24 | 24 |
| 1 | 3 | artist name | title c | water color on paper | 2002 | 01-01-2003 | 24 | 36 |
|------------------------------------------------------------------------

table port_images PRIMARY KEY (invID)(imgID)
-------------------------------------------------
| invID | imgID | full | large | medium | small |
|------------------------------------------------------------------------
| 1 | 1 | path/to/img a | path/to/img a | path/to/img a | path/to/img a |
| 2 | 1 | path/to/img b | path/to/img b | path/to/img b | path/to/img b |
| 3 | 1 | path/to/img c | path/to/img c | path/to/img c | path/to/img c |
| 2 | 2 | path/to/img c | path/to/img c | path/to/img c | path/to/img c |
|------------------------------------------------------------------------

table port_text PRIMARY KEY (invID)(txtID)
----------------------------------------------------
| invID | txtID | text | who | what | where | when |
|---------------------------------------------------
| 1 | 1 | text about work... | kw who | kw what | kw where | kw when |
| 2 | 1 | text about work... | kw who | kw what | kw where | kw when |
| 3 | 1 | text about work... | kw who | kw what | kw where | kw when |
| 1 | 2 | text about work... | kw who | kw what | kw where | kw when |
|---------------------------------------------------


Thanks