how can I choose a random number but with a normal probability distribution in PHP?

Question

In php, how can I generate a a random number assuming a normal distribution with a specific mean and standard devaition?

Answer 1

function nrand($mean, $sd){
    $x = mt_rand()/mt_getrandmax();
    $y = mt_rand()/mt_getrandmax();
    return sqrt(-2*log($x))*cos(2*pi()*$y)*$sd + $mean;
}