form submission with Javascript

Hello!
I am searching over the net for quite a long, but I have almost no idea concerning Javascript so I can't figure out the solution to my problem...
I have a form that show a drop-down menu, which takes all its values through a Mysql database via PHP. What I want to do is to submit the form to the next page (from index.php ---> retrieve_data.php) without the need of a "Submit" button.
When the user selects one of the given options, automatically he will be redirected to retrieve_data.php?id=5 for example...

Thank you in advance!

Call the document then the form then submit.

Code:

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document.FORMNAME.submit()

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For some reason this just doesn't work for me. If I click my button which launches this nothing happens.

Code:

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function submitForm()
{
  document.markForm.submit();
}

---

Code:

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<form method="post" name="markForm" id="markForm" action="update_entry.php">

---

Code:

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<input type="button" name="submit" value="Update Marks" class="SubmitButton" onClick="submitForm()" />

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I can't see anything wrong with that. My button takes the place of my submit as you can see.

Edited:
Eventually found out that I was getting this error in Firefox error console and looked it up:

"Error: document.markForm.submit is not a function"

What I found out is the the submit button with the name of "submit" can clash with the submit function. I changed the submit button's name and it worked fine.

You have the concept, it is done like you wrote. But little observation:

put

Code:

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onClick="submitForm();"

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instead of

Code:

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onClick="submitForm()"

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but i've no idea if it would fix the problem, since the error happen while submitting!