Calculates statistical information about an array of numbers, including upper and lower quartiles.

array_stats.php

<?php
function array_stats(array $arr) {
    sort($arr);
    
    // Basic data
    $result = array();
    $result['cnt'] = count($arr);
    $result['min'] = min($arr);
    $result['max'] = max($arr);
    $result['sum'] = array_sum($arr);
    $result['avg'] = $result['sum'] / count($arr);
    $result['med'] = $arr[round(count($arr) / 2)];
    $result['rng'] = $arr[$result['cnt'] - 1] - $arr[0];
    // Quartiles
    $result['qt1'] = $arr[round( .25 * ($result['cnt'] + 1)) - 1];
    $result['qt2'] = ($result['cnt'] % 2 == 0) ? (($arr[($result['cnt'] / 2) - 1] + $arr[$result['cnt'] / 2]) / 2) : ($arr[($result['cnt'] + 1) / 2]);
    $result['qt3'] = $arr[round( .75 * ($result['cnt'] + 1)) - 1];
    
    return $result;
}
?>