Querying External Dataset to Validate Number Input

I'm done some searching around the form and I'm just throwing this out there to see if anybody has any good ideas before I start doing anything with this. Here is the scenario:

1. I have a form where users have to enter their ID number.
2. I have a dataset that matches those ID numbers with their address.
3. I need to validate that the ID they enter is in fact an actual ID and not made up.
4. I also need to display their address on the screen below the ID field so they can make sure they input their ID correctly.

My dataset that I need to validate against is quite large (1,818 IDs). They are a 7 digit number that all start with 0 and range from 0071264 to 0584684 and are obviously not consecutive numbers (that really doesn't matter too much I suppose). I can put this dataset wherever I need to, in the WP database, csv or text file on the server, etc...

The ID number is the first thing they enter on the form and I need it to validate after they enter in their ID (not upon form submission).

I also have the form setup to redirect back to itself with half of the form being filled in automatically via query strings from the initial submission. The reason for this is users will be submitting the form anywhere from 1-10 times to register each person in their group. I realize that will require the form to revalidate the ID number when the form loads again after redirection and the fields are filled in via query strings.

So if you have any insight or if you've seen anybody do anything similar to this and wouldn't mind giving me a push start that would be awesome. Any other suggestions would be welcomed.

Thanks,
GB

Chris,

This definitely helps out a ton! I've got the code you supplied working on my form(s). I'm trying to expand it a little bit by using a csv file instead of just a list of IDs in a single column. Here is an example of my dataset.

I've got a script that I've stolen from php.net which splits this data from my text file into an array for each row and looks like this.

The output of that script against my data looks like this.

Is there any way you could help me marry your function with this csv to array script so it just searches the id's and the returns the three values within the matching ID's array as query strings?

Thanks,
GB

Still wrestling with this... anybody have an insight to my error I'm getting?

Chris,

Thanks for your reply. I've changed the ID as you described above. My 'ID' in this case won't change as that function will always be looking at just that ID of the first array value which is the first column in a text file. Anyway that did fix that issue.

You were right about the other issue with only passing one parameter in the first function. I'm a little confused on that. I think the "$_POST['input_1']" should be "$thiscode" in my is_code_valid function. I added the first two paramaters to the function call on line 8 but now it just validates false every time. I'm sure I'm just not connecting the dots properly.

Here is what things look like now: http://pastebin.com/UjxrLe4g

Thanks,
Grant