PHP: convert spaces in string into %20?
Use the rawurlencode function instead.
The plus sign is the historic encoding for a space character in URL parameters, as documented in the help for the urlencode() function.
That same page contains the answer you need - use rawurlencode() instead to get RFC 3986 compatible encoding.
I believe that, if you need to use the %20 variant, you could perhaps use rawurlencode().