(PECL stats >= 1.0.0)
stats_dens_gamma — Probability density function of the gamma distribution
$x
   , float $shape
   , float $scale
   ) : float
   Returns the probability density at x, where the
   random variable follows the gamma distribution of which the shape parameter
   is shape and the scale parameter is scale.
  
xThe value at which the probability density is calculated
shapeThe shape parameter of the distribution
scaleThe scale parameter of the distribution
   The probability density at x or FALSE for failure.