time-diff.php

<?php
/**
 * Return a singular or plural string based on the count provided
 *
 * @param string $singular The singular form
 * @param string $plural The plural form
 * @param string $count The count
 * @return string The appropriately translated string
 */
function plural($singular, $plural, $count) {
    return ($count == 1) ? $singular : $plural;
}

/**
 * time_diff function.
 *
 * Determines the difference between two dates.
 *
 * The difference is returned in a human readable format such as "1 hour",
 * "5 mins", "2 days", "1 hour and 32 seconds", depending on the precision level.
 *
 * You have 6 presicion levels, example since October 10, 1986:
 * - 1: "X years"
 * - 2: "X years and X months"
 * - 3: "X years, X months and X days"
 * - 4: "X years, X months, X days or X weeks and X hours"
 * - 5: "X years, X months, X days or X weeks, X hours and X minutes"
 * - 6: "X years, X months, X days or X weeks, X hours, X minutes and X seconds"
 *
 * @access public
 * @uses DateTime
 * @param string $from String in a format accepted by
 *                     {@link http://ca.php.net/strtotime strtotime()}
 * @param mixed $to (default: NULL) Date to end the time difference in a
 *                     format accepted by {@link http://ca.php.net/strtotime strtotime()}
 * @param int $precision (default: 1) The level of precision to return.
 * @return string Human readable time difference.
 */
function time_diff($from, $to = NULL, $precision = 1) {
    $from     = new DateTime($from);
    $to       = new DateTime($to);
    $interval = $from->diff($to);
    $suffix   = !$interval->invert ? ' ago' : ' more';

    $format = array();
    if ($interval->y !== 0) {
        $format[] = plural('%y year', '%y years', $interval->y);
    }

    if ($interval->m !== 0) {
        $format[] = plural('%m month', '%m months', $interval->m);
    }

    if ($interval->d !== 0) {
        if ($interval->d % 7 === 0) {
            $weeks = floor($interval->d / 7);
            $str = plural('%s week', '%s weeks', $weeks);
            $format[] = sprintf($str, $weeks);
        } else {
            $format[] = plural('%d day', '%d days', $interval->d);
        }
    }

    if ($interval->h !== 0) {
        $format[] = plural('%h hour', '%h hours', $interval->h);
    }

    if ($interval->i !== 0) {
        $format[] = plural('%i minute', '%i minutes', $interval->i);
    }

    if ($interval->s !== 0) {
        if (!count($format)) {
            return 'less than a minute ago';
        } else {
            $format[] = plural('%s second', '%s seconds', $interval->s);
        }
    }

    // Sets the precision
    if (count($format) > 1) {
        $format  = array_slice($format, 0, $precision);
        $last    = array_pop($format);
        $format  = implode(', ', $format);
        $format .= ($format == '') ? $last : ' and ' . $last;
    } else {
        $format = array_pop($format);
    }

    return $interval->format($format . $suffix);
}

$to   = date('r', strtotime('1 year, 1 month, 28 days, 30 minutes, 20 seconds ago'));
$diff = time_diff($to, NULL, 6);

var_dump($to, $diff);