Jimela - it depends. Different countries and different institutions have different requirements. It is not usually 'how many' (although a minimum may be stated) - but what is the quality and to what extent all disseminated, published sources are linked and related to each other and your specific topic for examination. The sources cannot be the same i.e. if the contents of a conference proceeding are mostly the same and included in a broader journal paper - then that content cannot be counted twice.

In most case i.e. PhD by Publication, PhD by Portfolio - it is not just the publications that are examined. They usually have to be accompanied with around a 20,000 word critical discourse that identifies their relatedness and the theoretical/philosophical framework that underpins them.

Jimela - it depends. Different countries and different institutions have different requirements. It is not usually 'how many' (although a minimum may be stated) - but what is the quality and to what extent all disseminated, published sources are linked and related to each other and your specific topic for examination. The sources cannot be the same i.e. if the contents of a conference proceeding are mostly the same and included in a broader journal paper - then that content cannot be counted twice.

In most case i.e. PhD by Publication, PhD by Portfolio - it is not just the publications that are examined. They usually have to be accompanied with around a 20,000 word critical discourse that identifies their relatedness and the theoretical/philosophical framework that underpins them.

Some university offers PhD by publications, usually they require three to four publication in peer reviewed good journals.

Yes, the portfolio would have to have been approved beforehand too

Awesome explanations. But Do I need a Primary supervisor if I am doing an online PHD Program?

Jimela Dora Kialo Yes. You must have a research supervisor. He/she acts as mentor, guide, advisor, tutor and internal examiner.

Completion conditions are dependent on your supervisor, or department, or Faculty, or University. So, better to discuss with your supervisor. I recommend you to publish at least two journal papers and a few conference proceedings during your PhD, since publications will be very important for you to apply for a research level job after completing your PhD. 

Thank you all for these awesome answers. I respect you as great mentors too!