date_diff.php

<?php
function getDateDiff($date)
{
    $diff_info=array();
    $timestamp=strtotime($date);
    $timestamp_diff=$timestamp-time();
    
    //test if $date is future
    $diff_info['future']=$timestamp_diff>0;

    $timestamp_diff=abs($timestamp_diff);
    
    //calculate total date difference
    $date_diff=round($timestamp_diff/(24*3600));

    //year
    $diff_info['year']=floor($date_diff/365);
    $date_diff-=$diff_info['year']*365;

    //month
    $diff_info['month']=floor($date_diff/30.5);
    $date_diff-=floor($diff_info['month']*30.5);

    //day
    $diff_info['day']=$date_diff;

    return $diff_info;
}

test.php

<?php
$diff=getDateDiff('8/12/2012');
if($diff['future'])
{
    echo "You have {$diff['year']} year(s), {$diff['month']} month(s), {$diff['day']} day(s) left";
}
else
{
    echo "Your account has expired";
}