Hacked this up a couple years back for someone to show data usage from a local RADIUS file system database on pfSense.

radius-accounting.php

<?php

//online time
//sessions

$logdir = '/var/log/radacct/192.168.1.1';

$users = array();
$packets = array();

function format_bytes($b, $p=null) {
    $units = array("B","kB","MB","GB","TB","PB","EB","ZB","YB");
    $c=0;
    if(!$p && $p !== 0) {
        foreach($units as $k => $u) {
            if(($b / pow(1024,$k)) >= 1) {
                $r["bytes"] = $b / pow(1024,$k);
                $r["units"] = $u;
                $c++;
            }
        }
        return number_format($r["bytes"],2) . " " . $r["units"];
    } else {
        return number_format($b / pow(1024,$p)) . " " . $units[$p];
    }
}

if ($dir = opendir($logdir)) {
    while (false !== ($file = readdir($dir))) {
        if (strpos($file, 'detail-') === false) {   
            continue;
        }

        $handle = fopen($logdir.'/'.$file, 'r');
        while (!feof($handle)) {
            $buffer = fgets($handle, 4096);

            // Match empty lines
            if (strlen(trim($buffer)) == 0) {
                continue;
            }

            // Match lines that don't start with tabs
            if ($buffer{0} != "\t") {
                if (isset($packet['type'])) {
                    $packets[] = $packet;
                }
                $packet = array();
            }

            if (strpos($buffer, 'Acct-Status-Type')) {
                $bits = explode(' = ', $buffer);
                $data = trim($bits[1]);
                $packet['type'] = $data;
            }
            if (strpos($buffer, 'User-Name')) {
                $bits = explode(' = ', $buffer);
                $data = str_replace('"', '', trim($bits[1]));
                $packet['user'] = $data;
            }
            if (strpos($buffer, 'Acct-Input-Octets')) {
                $bits = explode(' = ', $buffer);
                $data = trim($bits[1]);
                $packet['input_octets'] = $data;
            }
            if (strpos($buffer, 'Acct-Output-Octets')) {
                $bits = explode(' = ', $buffer);
                $data = trim($bits[1]);
                $packet['output_octets'] = $data;
            }
            if (strpos($buffer, 'Acct-Input-Gigawords')) {
                $bits = explode(' = ', $buffer);
                $data = trim($bits[1]);
                $packet['input_gigawords'] = $data;
            }
            if (strpos($buffer, 'Acct-Output-Gigawords')) {
                $bits = explode(' = ', $buffer);
                $data = trim($bits[1]);
                $packet['output_gigawords'] = $data;
            }
        }
        fclose($handle);
        // Grab the last packet
        if (isset($packet['type'])) {
            $packets[] = $packet;
        }
    }
}

foreach ($packets as $packet) {
    if ($packet['type'] == 'Stop') {
        if (empty($users[$packet['user']])) {
            $users[$packet['user']] = array(
                'in' => 0, 
                'out' => 0, 
                'total' => 0, 
            );
        }
        $bytes_in = $packet['input_octets'];
        $bytes_out = $packet['output_octets'];
        if (!empty($packet['input_gigawords'])) {
            $bytes_in += ($packet['input_gigawords'] * 4294967296);
        }
        if (!empty($packet['output_gigawords'])) {
            $bytes_out += ($packet['output_gigawords'] * 4294967296);
        }
        $users[$packet['user']]['in'] += $bytes_in;
        $users[$packet['user']]['out'] += $bytes_out;
        $users[$packet['user']]['total'] += $bytes_in + $bytes_out;
    }
}

foreach ($users as $user => $info) {
    print "$user: ".format_bytes($info['total']).' ('.format_bytes($info['in']).'/'.format_bytes($info['out']).")\n";
}

?>