瑞士的博士多少年？
PhD in Switzerland is mostly 4-7 years long， depending on the university and department. You can find a rough guide about the length of PhD studies at this link (in German). The duration is given as “from 3’600 to 5’100 teaching hours” corresponding to four or six academic years respectively. A teaching hour is defined as an hour of lectures followed by an hour of seminars/tutorials， with one or two contact hours per week for each student and a total of 220 hours a year（相当于国内大学一个学期）。
A PhD candidate who does not complete his/her thesis by the end of this time limit will have to reapply for admission to continue with his/her research， and will be required to do so within certain time limits after receiving his/her master's degree. In such cases， it might even take longer than seven years until you defend your thesis and obtain your PhD. ⚠️ Note that this link only gives information about the maximum amount of time required to complete a PhD. However， most students finish much earlier than that， usually between three and five years from the beginning of their PhD programme.
A PhD program consists of two main parts： first you write up a Master's Thesis based on your MA research， which has to be completed within the standard timeframe， then you start working on your own original scientific research project， which leads to your final doctoral dissertation. Your PhD thesis must contain original contributions to knowledge and show an advanced understanding of contemporary developments in your field of study.
The application process to begin a Phd Programme is described here (in English). You can apply through universities directly or go via education agencies if you wish； I would personally advise going direct because you don't need to pay any fees！
You are assessed according to your Master's Thesis， and if accepted， you will be formally admitted into the Graduate School and receive a letter informing you of the University's decision. Before starting work on your PhD， you will also need to select a supervisory team of professors who will guide you throughout your research and help prepare you for the viva voce