file.php

<?php
require_once 'NikePlusPHP.php';

function login($user,$pass){
    $n = new NikePlusPHP($user, $pass);
    return $n;
}

function flatten(array $array) {
    $return = array();
    array_walk_recursive($array, function($a) use (&$return) { $return[] = $a; });
    return $return;
}

function prettyPrint($a) {
    echo '<pre>'.print_r($a,1).'</pre>';
}

$login = login("[email protected]",XXXXXXX);

$fuel = $login->activities(2); // this line got the info above from web service, 

$test = flatten($fuel);
prettyPrint($test[0]);

echo($test[0]->name ); // RUN ON: 04/05/15 02:22 PM
echo($test[0]->tags->SHOES->name); // New running sho

var_dump($tags);
?>

output

stdClass Object
(
    [name] => RUN ON: 04/05/15 02:22 PM
    [activityId] => 4038000000016924187710009732248116689150
    [activityType] => RUN
    [appId] => CONNECT
    [timeZone] => +01:00
    [timeZoneId] => GMT+01:00
    [dstOffset] => 00:00
    [startTimeUtc] => 2015-04-05T14:22:32+01:00
    [status] => complete
    [activeTime] => 0
    [gps] => 1
    [latitude] => 52.44516
    [longitude] => -1.929284
    [heartrate] => 
    [deviceType] => SPORTWATCH
    [tags] => stdClass Object
        (
            [SHOES] => stdClass Object
                (
                    [name] => New running sho
                    [distance] => 524.12817977264
                    [activityCount] => 56
                    [percentage] => 19.377162629758
                    [retired] => 
                )

        )

    [metrics] => stdClass Object
        (
            [duration] => 3219000
            [calories] => 728
            [fuel] => 2564
            [steps] => 0
            [distance] => 9.9973001480103
        )

)