Generic structuration of a web form and a MySQL's table for saving a array of undefined length

In a web form i will ask the user for their job experiences, this data will have no fixed lenght. I need to let the user insert all the items he needs, every item will content 3 fields; job title, description and year.

My firts problem is, how can i ask in the html form for the items? i mean, whats the best way to ask items with no fixed lenght using html/php (and maybe ajax)? I saw some sites that have a button (add one) when you hit it a new item slot is showed, but i have no idea of how to implement this, an example will be sufficient.

The second part is, how can i managed the data flow in post or get?, until now, i only use fixed fields, so i always know in my php script how many post or get vars i will get. How can i use multiple POST vars without knowing the amou开发者_运维百科nt of them?

And the last one (and the more important), how will be the best structure for my table in MySQL? If i get multiple items for a fixed table where i will have all my users, how can i resolve the multiple items issue? For example, if my table is:

User  |   password    |    job_experiences
admin |   root        |    (this is just a cell, how can i save multiple items here?)    
jonh  |   1234        |    (this is just a cell, how can i save multiple items here?)

Thanks for any help!!!!

Those are 3 questions, and it's best to post 3 questions, instead of discussing all of them. I will post the basics, and if you have specific questions, ask.

First, use button to add, and a JavaScript to clone an existing row (which can have more then one input field). For fieldnames use something like company_name[] - the [] is the important part, at this will send the field as an array. If you are editting profile, you can use company_name[$id] to preserve the mapping.

Second, in PHP you will receive this as $_POST['company_name'] which will be numeric array with all the company names. Or if you specify $id - with the corresponding keys. So, you have to loop trough all company_names, if there are other fields - you retrieve them the same way, using the current key. Example:

for (i =0; i<$_POST['comany_name'].length;i++) {
   $company = $_POST['comany_name'][$i];
   $start_year = $_POST['from'][$i];
   ...
}

Next, you need 1 table for the users (username, password), and another for job experiences (userid, company, description, from, to). This is called 1:M relation