Get number of days between 2 dates

date.php

<?php

if (count($argv)<=1) {
    return usage();
}

$format = 'm/d/Y h:i A';
if (isset($argv[3])) {
    $format = $argv[3];
}
$date1 = DateTime::createFromFormat($format, $argv[1]);
$date2 = DateTime::createFromFormat($format, $argv[2]);

if (!($date1 || $date2)) {
    echo "\nInvalid input dates or invalid input format\n\n";
    return;
}

$dDiff = $date2->diff($date1);
echo $dDiff->format('%R');
echo $dDiff->days." days\n";

function usage()
{
    echo "\nphp date.php [date1] [date2] [optional:format]\n\n";
}