The proportional hazards (PH) model specifies distributions for regression data. Given a covariate value, the PH model specifies a family of distributions for a random variable, called the PH family. I will talk about the method of generating pseudo random numbers under various special cases when the random variable may take infinity with probability one. I will also talk about the identifiability condition of the parameters in the PH family and the semi-parametric estimation of the parameters under the identifiability condition.