How many years does it take to complete PhD in Korea?

I'm curious to know, how many years does it typically take for someone to complete a PhD program in Korea? I've heard that the duration can vary depending on the field of study and the university, but I'm looking for a general idea. Does the process follow a standard timeline, or are there any factors that can affect the length of the program? Additionally, what kind of requirements and milestones do students need to meet in order to progress through the program and ultimately earn their PhD?