Parse a twitter archive csv to pull out the time stamps

twitter.php

<?php
date_default_timezone_set('America/New_York');
$file = $argv[1];
$all = '';
$tweets = '';
$retweets = '';
if (($handle = fopen($file, "r")) !== FALSE) {
    while (($data = fgetcsv($handle, 0, ",")) !== FALSE) {
        $str = strtotime($data[5])."\n";
        $all .= $str; 
        if ($data[3])
            $retweets .= $str;
        else
            $tweets .= $str;
    }
}                                                                                                                                 
echo $tweets;