  In this paper we study the quantum phase properties of {\it "nonlinear
coherent states"} and {\it "solvable quantum systems with discrete spectra"}
using the Pegg-Barnett formalism in a unified approach. The presented procedure
will then be applied to few special solvable quantum systems with known
discrete spectrum as well as to some new classes of nonlinear oscillators with
particular nonlinearity functions. Finally the associated phase distributions
and their nonclasscial properties such as the squeezing in number and phase
operators have been investigated, numerically.
