I'm familiar with the convention of using hyphens to separate words in URL paths. What about parameter names, such as within a <form>:
<form>
<input name="my_special_field">
</form>
is that better or my-special-field? I've seen Google use underscores in analytics with utm_campaign and other parameter names. Underscores read a little better and allow for the occasional hyphen within the name (field_for_5-16-17). But hyphens are certainly the convention for URL paths.
What's the convention for separating words in an HTTP parameter name?