What RFC defines arrays transmitted over HTTP?

Question

What RFC defines the passing arrays over HTTP? Most web application platforms allow you to supply an array of arguments over GET or POST. The following URL is an example:

http://localhost/?var[1]=one&var[2]=two&var[3]=three

RFC1738 defines URLs, however the bracket is missing from the Backus–Naur Form(BNF) definition of the URL. Also this RFC doesn't cover POST. Ideally I would like to get the BNF for this feature as defined in the RFC.

Answer 1

According to Wikipedia, there is no single spec:

While there is no definitive standard, most web frameworks allow multiple values to be associated with a single field (eg. field1=value1&field1=value2&field2=value3)

That Wikipedia article links to the following Stack Overflow post, which covers a similar question: Authoritative position of duplicate HTTP GET query keys

The issue here is that form parameters can be whatever you want them to be. Some web frameworks have settled on key[number]=value for arrays, others haven't. Interestingly, RFC1866 section 8.2.4, page 48 (note: this RFC is historical and not current) shows an example with the same key used twice in a form POST:

name=John+Doe
&gender=male
&family=5
&city=kent
&city=miami
&other=abc%0D%0Adef
&nickname=J%26D

On the W3C side of things, HTML 4.01 has some information about how to encode form parameters. Sadly this doesn't cover arrays.

At the time of writing, I don't think there is a correct answer to your question - no IETF RFC or W3C spec defines the behavior that you're interested in.

(As a side note, the W3C HTML JSON form submission draft spec covers posting arrays, thank goodness.)