<?php
function prettyDate($date){
  $time = strtotime($date);
  $now = time();
  $ago = $now - $time;
  if($ago < 60){
    $when = round($ago);
    $s = ($when == 1)?"second":"seconds";
    return "$when $s ago";
  }elseif($ago < 3600){
    $when = round($ago / 60);
    $m = ($when == 1)?"minute":"minutes";
    return "$when $m ago";
  }elseif($ago >= 3600 && $ago < 86400){
    $when = round($ago / 60 / 60);
    $h = ($when == 1)?"hour":"hours";
    return "$when $h ago";
  }elseif($ago >= 86400 && $ago < 2629743.83){
    $when = round($ago / 60 / 60 / 24);
    $d = ($when == 1)?"day":"days";
    return "$when $d ago";
  }elseif($ago >= 2629743.83 && $ago < 31556926){
    $when = round($ago / 60 / 60 / 24 / 30.4375);
    $m = ($when == 1)?"month":"months";
    return "$when $m ago";
  }else{
    $when = round($ago / 60 / 60 / 24 / 365);
    $y = ($when == 1)?"year":"years";
    return "$when $y ago";
  }
}
echo prettyDate("2012-07-22 12:23:45")."<br />";
echo prettyDate("2010-11-12 22:25:45")."<br />";
echo prettyDate("2012-01-01 01:00:00")."<br />";
echo prettyDate("2001-05-30 00:00:00")."<br />";