(PECL stats >= 1.0.0)
stats_dens_normal — Probability density function of the normal distribution
$x
   , float $ave
   , float $stdev
   ) : float
   Returns the probability density at x, where the
   random variable follows the normal distribution of which the mean is
   ave and the standard deviation is
   stdev.
  
xThe value at which the probability density is calculated
aveThe mean of the distribution
stdevThe standard deviation of the distribution
   The probability density at x or FALSE for failure.