Usually, a PhD student publish the results of the PhD research. Although the research description should be in your PhD thesis. Specifically, Publishing requires writing up your research findings in the form of a journal article. Then, submit it to one of the specialized journals within your field. To understand why publishing determines which PhD students will become future academics, we can compare it to the concept of Natural Selection. In this case, competition for academic position is intense. And so, publishing Journal Paper is used to select those students who stand out and separate them from the rest. Because, the publishing process is highly competitive and to publish in a high quality journal requires you to compete against other researchers.