Publishing articles in not peer-reviewed journals There are several important journals out there that are not peer-reviewed, such as Network Security. Do such papers provide any value for the author(s), especially for whom want to apply for a PhD program.
You call them "important journals". Others would call them "magazines". Most fields have them and "recognized experts" can present useful information to practitioners. But they seem to be more "popularizers of field X" than true journals. Their only control is editorial. For a recognized expert, they probably have a bit of value come time for salary and promotion decisions as they may give an indication of the external reputation of a person. 

I think that if a person writes a research paper sufficient for publication in a peer-reviewed journal, they would do send it for peer review. They wouldn't submit it to a non-peer-reviewed place at all. On the other hand, a "layman's" or "practitioners" article on the consequences of the research would be suitable for such a journal, but it would be backed by the earlier research publication. Likewise, if a person does some work, but it isn't up to the standards of a peer reviewed journal, but has important applications, it would be good to get it out there for practitioners. But, by definition, it isn't up to par for the peer reviewed journal. 

Therefore, for entry to a doctoral program, I think they would have very little value. The problem is in the analysis of the work. If you publish in a peer reviewed journal, someone evaluating your CV can depend on the quality of the work because they know about the system and how it works. They can trust that experts in the field have looked closely at the work and judged it worthy. That isn't the case with non-peer-reviewed work. Therefore they would need to evaluate the work themselves and would not be especially willing to do so. 

The Elsevier series you mention is, perhaps, a bit better than a magazine, but not like a true "journal." Publishing here is unlikely to hurt you, as some other things might (predatory journals), but won't help much. You will need the rest of your CV to be adequate to support your candidacy. 



Caveat: The above is opinion. It is how I would look at the CV of a candidate, nothing more. You would still have to make your case otherwise.