Giving a bash script the option to accept flags like a command [duplicate]

Question

I'm writing a simple bash script and I would like it to accept parameters from the command line in any order.

I've browsed around the web and wrote a simple function with a case statement in a while loop. Right now, the 'any order' part works - but it only picks up the first parameter I set. I'm certainly doing something wrong but scripting is quite new to me and I hadn't been able to figure it out - your help would be greatly appreciated. The flags part of the script is as follows:

#Parameters - source,destination,credentials,bandwidth,timeout,port,help
flags () {
        while test $# -gt 0; do
                case "$1" in
                        -s|--source)
                                shift
                                if test $# -gt 0; then
                                        export SOURCE=$1
                                else
                                        echo "No source directory specified!"
                                        exit 1
                                fi
                                ;;
                        -d|--destination)
                                shift
                                if test $# -gt 0; then
                                        export DESTINATION=$1
                                fi
                                ;;
                        -c|--credentials)
                                shift
                                if test $# -gt 0; then
                                        export CREDENTIALS=$1
                                fi
                                ;;
                        -b|--bandwidth)
                                shift
                                if test $# -gt 0; then
                                        export BANDWIDTH=$1
                                fi
                                ;;
                        -t|--timeout)
                                shift
                                if test $# -gt 0; then
                                        export TIMEOUT=$1
                                fi
                                ;;
                        -p|--port)
                                shift
                                if test $# -gt 0; then
                                        export PORT=$1
                                fi
                                ;;
                        -h|--help)
                                shift
                                if test $# -gt 0; then
                                        echo "Help goes here"
                                fi
                                ;;
                        -l|--compression-level)
                                shift
                                if test $# -gt 0; then
                                        export COMPRESS_LEVEL=$1
                                fi
                                ;;
                        *)
                                break
                                ;;
                esac
        done
}
flags "$@"
echo "source is $SOURCE, destination is $DESTINATION, credentials are $CREDENTIALS, bandwidth is $BANDWIDTH, timeout is $TIMEOUT, port is $PORT"

Ideally, some of those parameters would be mandatory, and others optional - but that's not a must.

How can I fix this script to accept any of those parameters (both long and short forms, ideally) in any order?