PHP for calculating the mean and standard deviation of an array

<?php

// Define the array
$data = [1, 2, 3, 4, 5];

// Calculate the mean
$mean = array_sum($data) / count($data);

// Calculate the standard deviation
$sum = 0;
foreach ($data as $value) {
    $distance_from_mean = $value - $mean;
    $sum += pow($distance_from_mean, 2);
}
$standard_deviation = sqrt($sum / count($data));

// Print the results
echo "Mean: $mean\n";
echo "Standard deviation: $standard_deviation\n";

?>

This code calculates the mean and standard deviation of an array using the following formulas:

Mean = sum of all values / number of values
Standard deviation = sqrt(sum of (distance from mean)^2 / number of values)

To calculate the mean, we use the array_sum() function to sum all the values in the array, and then divide the result by the number of values in the array.

To calculate the standard deviation, we first calculate the distance of each value from the mean. Then, we square each of these distances and sum them up. Finally, we divide this sum by the number of values in the array and take the square root to get the standard deviation.

This code is effective because it is simple and easy to understand, and it can be used to calculate the mean and standard deviation of any array of values.