You should ask your supervisor as it depends on him/her if it's enough or not. A quite good estimate might be publications...for a phd 2-3 peer-reviewed papers surely "secure" this or are even needed, depending on the doctoral regulations. This means (unfortunately) that you have to produce new, interesting results which are publishable...this is or can be a difference to master degree, where students sometimes just try out something (with unknown perhaps no results) or establish a technique and the results are anyway published earlier.
Anyway very few lucky dudes don't need to work more than a master student, if everything works perfect and the topics are so "sexy" that you can even publish a few results...
In a nutshell: not the quantity but more the quality is important for phd theses (though some supervisors want both).
One must presume that long and short arguments contribute to the same end. - Epicurus
...except casandra's that did belong to the funniest, most interesting and imaginative (or over-imaginative?) ones, I suppose.