(PECL stats >= 1.0.0)
stats_dens_chisquare — Probability density function of the chi-square distribution
$x, float $dfr): float
   Returns the probability density at x, where the
   random variable follows the chi-square distribution of which the degree of
   freedom is dfr.
  
xThe value at which the probability density is calculated
dfrThe degree of freedom of the distribution
   The probability density at x or false for failure.