If you can't use PECL can you use PEAR?
If so, there is a decent basic stats package for PEAR. This library can calculate: min, max, sum, count, mean, median, mode, midrange, geometric mean, harmonic mean,
STANDARD DEVIATION, absolute deviation,
VARIANCE, range, standard error of mean, skewness, kurtosis, coeff of variation, sample central moments, sample raw moments, frequency, quartiles, interquartile range, interquartile mean, quartile deviation, quartile variation coefficient, quartile skewness coefficient
With this foundation and some coding work (alright, probably a fair bit of coding work), you could come up with a script for looking at your confidence intervals. I haven't had to work with confidence intervals in PHP, having happily been able to take Mplus and SPSS for granted, so I don't really have much of a suggestion on a starting point for the confidence intervals.
Hope this helps!
THE PEAR PACKAGE:
http://pear.php.net/package/Math_Stats/download/
