In Extending the Smarty Template Engine I outlined the steps needed to create all the varieties of plugins for the Smarty template engine. Continuing with that tutorial, and to provide a little context, here’s a quick Smarty plugin for converting timestamps into relative timestamps.

This is a Smarty module plugin; notice how the name conforms to the naming conventions with the prefix “smarty_modifier_”

<?php
/**
 * Smarty plugin
 * @package Smarty
 * @subpackage plugins
 */

/**
 * Smarty relative date / time plugin
 *
 * Type:     modifier

 * Name:     relative_datetime

 * Date:     March 18, 2009
 * Purpose:  converts a date to a relative time
 * Input:    date to format
 * Example:  {$datetime|relative_datetime}
 * @author   Eric Lamb 
 * @version 1.0
 * @param string
 * @return string
 */
function smarty_modifier_relative_datetime($timestamp)
{
	if(!$timestamp){
		return 'N/A';
	}

	$timestamp = (int)strtotime($timestamp);
	$difference = time() - $timestamp;
	$periods = array("sec", "min", "hour", "day", "week","month", "year", "decade");
	$lengths = array("60","60","24","7","4.35","12","10");
	$total_lengths = count($lengths);

	if ($difference > 0) { // this was in the past
		$ending = "ago";
	} else { // this was in the future
		$difference = -$difference;
		$ending = " from now";
	}
	//return;

	for($j = 0; $difference > $lengths && $total_lengths > $j; $j++) {
		$difference /= $lengths;
	}

	$difference = round($difference);
	if($difference != 1) {
		$periods.= "s";
	}

	$text = "$difference $periods $ending";

	return $text;
}

Installation

Just copy the contents above and paste into a file called:
modifier.relative_datetime.php

Place the file in your Smarty plugin directory and you’re good to go.

Usage Example:

{$item.timestamp|relative_datetime}