Get percentage of time that the CPU was idle from sar command as JavaScript variable

get-sar.php

<?php

/**
 * Place this PHP script somewhere accessible via HTTP, amend it for your situation if necessary
 *
 * Example Usage with jQuery
 * $.getScript(
 *     'http://my-site.com/get-sar.php',
 *     function() {
 *         // You can use something like http://www.chartjs.org/ to display the data as chart
 *         console.log(sarData.data[0].time);
 *         console.log(sarData.data[0].idle);
 *         console.log(sarData.avg.idle);
 *     }
 * );
 */

$sar = '/usr/bin/sar -u'; // You may have to amend here

exec($sar, $sarResults);
// var_dump($sarResults); exit;

$data = array();

foreach ($sarResults as $r) {
    if (strpos($r, 'Linux') !== false) continue;
    if ($r == '') continue;
    sscanf($r, "%s%s%s%s%s%s%s%s\n", $time, $cpu, $user, $nice, $system, $iowait, $steal, $idle);
    if ($cpu == 'CPU') continue;
    if ($time == 'Average:') {
        $data['avg'] = $idle;
        continue;
    }
    // echo $time . $cpu . $user . $nice . $system . $iowait . $steal . $idle . "\n";
    $data['data'][] = array(
        'time' => $time,
        'idle' => $idle,
    );
}

header('Content-Type:text/javascript; charset=utf-8');
echo 'var sarData = ' . json_encode($data) . ';';