Most professions don’t require an PhD. Lawyers, engineers and business people — for example — rarely feel it is worth the investment. The time to complete such a degree varies considerably. In most fields, students who already have an undergraduate degree (S1) require at least four years of additional coursework, research and practical experience in order to quality for a PhD.
On the other hand, students whose aim is to develop a high level of expertise in order to be teach others, conduct research or serve in a high-level, must invest the additional years in order to be qualified for work opportunities.
PhD programs vary considerably from one country to another and from university to university. In general, one must demonstrate proficiency is research and writing. A PhD candidate generally must submit a his research (also known as a thesis or dissertation) for approval by a committee of senior academics. In situations where all coursework (classes and other specific requirements) are completed but the research has not been approved, the candidate takes an unofficial status known as ABD — “all but dissertation.”