Create nicely formatted timestamps in php

nice_time_ago.php

<?php

    	/**
	 *
	 * Creates nicely formated timestamps
	 *
	 * @param timestamp $date
	 * @return string 
	 */
	public static function get_x_time_ago($date) 
	{
		if(empty($date))
	        return "No date provided";
	    
		$periods         = array("second", "minute", "hour", "day", "week", "month", "year", "decade");
		$lengths         = array("60","60","24","7","4.35","12","10");

		$now             = time();
		$unix_date         = strtotime($date);

		// check validity of date
		if(empty($unix_date))  
		return "Bad date";

		// is it future date or past date
		if($now > $unix_date) 
		{    
			$difference     = $now - $unix_date;
			$tense         = "ago";

		} 
		else 
		{
			$difference     = $unix_date - $now;
			$tense         = "from now";
		}

		for($j = 0; $difference >= $lengths[$j] && $j < count($lengths)-1; $j++) 
		{
			$difference /= $lengths[$j];
		}

		$difference = round($difference);

		if($difference != 1) 
		{
			$periods[$j].= "s";
		}

		return "$difference $periods[$j] {$tense}";
	}