When should space be encoded to plus (+) or %20?
urlencode
Solution
`+` means a space only in `application/x-www-form-urlencoded` content, such as the query part of a URL:
http://www.example.com/path/foo+bar/path?query+name=query+value
In this URL, the parameter name is `query name` with a space and the value is `query value` with a space, but the folder name in the path is literally `foo+bar`, not `foo bar`.
`%20` is a valid way to encode a space in either of these contexts. So if you need to URL-encode a string for inclusion in part of a URL, it is always safe to replace spaces with `%20` and pluses with `%2B`. This is what, e.g., `encodeURIComponent()` does in JavaScript. Unfortunately it's not what urlencode does in PHP (rawurlencode is safer).
See Also
HTML 4.01 Specification application/x-www-form-urlencoded
Problem
Sometimes the spaces get URL encoded to the `+` sign, and some other times to `%20`. What is the difference and why should this happen?