Online Computer Science Masters as PhD Prep
These are professional masters programs.

My department (Illinois) does not consider even our own online MCS program to be preparation for a PhD, because there is no requirement—and therefore in practice almost no opportunity—for research experience.

Moreover, it is unlikely that any instructor of an online course can provide useful recommendation letters for their students for PhD programs, because useful letters generally require direct, personal, one-on-one interaction.  Sure, they can write a letter describing your class performance, but such letters are nearly useless; we can already see your grades on your transcript.