When writing about a person who holds a doctorate of philosophy degree, the designation "Ph.D." traditionally follows his name. This way, readers can easily understand his qualifications and authority. Punctuating this marking can seem a bit complex, especially since different people write it differently. Standard rules do apply to this issue, but the most important thing is consistency; however you punctuate it, do it the same way throughout your paper, article or document.
Type the person's full name--for example, "Jane Smith."
Type a comma, then type a space.
Type "Ph.D." Capitalize the "P" and the "D," but write the "h" in lowercase. Put a period after the "h" and after the "D," and do not type a space between the "h" and the "D."
Type another comma immediately after the second period in "Ph.D.," and then type a space. Now continue writing as you would normally, for example, "Jane Smith, Ph.D., earned an award for her research in psychology." Or, if the sentence ends with the "Ph.D." designation, then simply move on to the next sentence; you do not need to add another period. For example, "The institute gave the award to Jane Smith, Ph.D. Smith recently finished her research study in psychology."