PHP Multidimensional Array Sort array_reverse not working?

I have a Multidimensional array that I am trying feverishly to properly sort by the date.

So far I've got:

usort($respArr, function($a, $b){
        $t1 = strtotime($a['PublishDate']);
        $t2 = strtotime($b['PublishDate']);
        return $t1 - $t2;
    });

array_reverse($respArr);
echo '<pre>';
print_r($respArr);
echo '</pre>';
echo '<hr />';

Here's some of the output from the above:

Array
(
[34] => Array
    (
        [Title] => o7thwd: Partnered with Internet Services Inc., to offer complete online presence! http://t.co/1SgAF66Tbf @ISI_Cloud
        [Link] => http://twitter.com/o7thwd/statuses/306088158574022656
        [PublishDate] => 2/25/2013 12:07:58 PM
        [Image] => 
        [Description] => o7thwd: Partnered with Internet Services Inc., to offer complete online presence! http://t.co/1SgAF66Tbf @ISI_Cloud
    )

[35] => Array
    (
        [Title] => o7thwd: Hangin with Mama Bear giving her the basics of social networking
        [Link] => http://twitter.com/o7thwd/statuses/307916797066240000
        [PublishDate] => 3/2/2013 1:14:19 PM
        [Image] => 
        [Description] => o7thwd: Hangin with Mama Bear giving her the basics of social networking
    )

[36] => Array
    (
        [Title] => o7thwd: o7th Web Design Articles http://t.co/plP8OkB7So
        [Link] => http://twitter.com/o7thwd/statuses/308687737400205313
        [PublishDate] => 3/4/2013 4:17:46 PM
        [Image] => 
        [Description] => o7thwd: o7th Web Design Articles http://t.co/plP8OkB7So
    )

[37] => Array
    (
        [Title] => o7thwd: finished up my GUI for a YUI minifier: http://t.co/7DKLoCXJHw
        [Link] => http://twitter.com/o7thwd/statuses/309309871931682816
        [PublishDate] => 3/6/2013 9:29:54 AM
        [Image] => 
        [Description] => o7thwd: finished up my GUI for a YUI minifier: http://t.co/7DKLoCXJHw
    )

[38] => Array
    (
        [Title] => o7thwd: o7th Web Design Articles http://t.co/QAIUO2Qjko
        [Link] => http://twitter.com/o7thwd/statuses/314356123027243008
        [PublishDate] => 3/20/2013 8:41:54 AM
        [Image] => 
        [Description] => o7thwd: o7th Web Design Articles http://t.co/QAIUO2Qjko
    )

[39] => Array
    (
        [Title] => SkorIn2: starting new desktop app to compliment the web app
        [Link] => http://twitter.com/SkorIn2/statuses/314718985725804545
        [PublishDate] => 3/21/2013 8:43:48 AM
        [Image] => 
        [Description] => SkorIn2: starting new desktop app to compliment the web app
    )

)

However, the array is not reversed, as you can tell above. Can anyone help me with this?
It's showing me that the array is indeed sorted by the 'PublishDate', however, in the reverse order that I need it in.

The actual problem is you're not assigning the result of array_reverse to anything

// change this
array_reverse($respArr);

// to this
$respArr = array_reverse($respArr);