Functions for scanning command line options
The bash code all looks reasonably fine to me.

The -h and --help output doesn't look right (it will print the actual parameters passed, but should print the list of allowable options/parameters?)

Options like --this-will-break won't work with --will or --break.

I'm not clear if parameters with spaces in them will work, as in: testmygetopts "this is one argument"

I think 'isoption' could be simplifed to just be the [[ ]] expression (since it will return 0 or 1 already).