Flickr provides a neat little snippet of javaScript to supply various image galleries direct to your site – a so-named Flickr badge.

So if your gallery is on Flickr – rather in your WordPress, which has its own gallery shortcode – a shortcode in the blog post content can be used to embed a gallery of thumbnail images, which is also a good way to demonstrate the various usages of WordPress shortcodes.

The HTML for a flickr badge looks something like this:-

<div class="flickr_badge"><script type="text/javascript" src="http://www.flickr.com/badge_code_v2.gne?count=5&display=latest&size=m&layout=h&source=all_tag&tag=fish"></script></div>

And the parameters work like this:-

count integer 1-10. Default is 10.

display string ‘latest’ or ‘random’ Default is latest.

layout string h, v, x - Photos are listed horizontally, vertically, or no style. Default is horizontal.

source string user, user_tag, user_set, group, group_tag, all, all_tag

Source implies which ‘account’ the photos come from:- a specified user, a user set, a group, or all users, then filtered by tag if required. Further parameters may then be required, user(ID string) tag (string), group (integer), and set (integer, the url …/sets/1234567/).

size string s, t, m s stands for square (cropped, not small…), t for thumbnail, and m for medium. t = thumbnail is the default.

(idgettr is very useful for figuring out user IDs and the IDs for photosets, groups etc.)

WordPress Shortcodes

A shortcode has a “handler function” – which is integrated into the code by calling the function add_shortcode(). The purpose here is to supply the various parameters for our Flickr badge as parameters of the function – the query string for the Flickr call is then constructed and the javascript code output to the page.

In functions.php

function flickr_badge_shortcode($atts){

//Here's our defaults
$query_atts = shortcode_atts(array('count' => '6', 'display' => 'latest', 'source' => 'user', 'size' => 't', 'user' => '', 'layout' => 'x', 'tag' => '', 'group' => '', 'set' => ''), $atts); 

 	return sprintf('<div class="flickr_badge"><script src="http://www.flickr.com/badge_code_v2.gne?%s" type="text/javascript"></script></div>
', http_build_query($query_atts));
}

add_shortcode('flickrbadge', 'flickr_badge_shortcode');

Provided you have PHP5 on the server, http_build_query() is the quick and easy way of building a query string from an array – and it’s urlencoded….

Note that the empty parameters group, set etc. are required in the defaults – otherwise nothing gets passed to the constructed url via shortcode_atts().

So now, in a post content you can apply the shortcode tag:

[flickrbadge count="4" layout="h" display="latest" size="t" source="all_tag" tag="fish"]

And you should get a nice gallery of Flickr images for users to check out – once you’ve added some CSS to style the images (note the possible uses of the layout parameter here).

This example was of the selfclosing shortcode tag – but you can elaborate a bit, to inject more content into the shortcode function. The simplest example would be to give the gallery a custom title.

Again in functions.php

function flickr_badge_shortcode($atts, $content=NULL){

//Here's our defaults
$query_atts = shortcode_atts(array('count' => '6', 'display' => 'latest', 'source' => 'user', 'size' => 't', 'user' => '', 'layout' => 'x', 'tag' => '', 'group' => '', 'set' => ''), $atts);

return sprintf('<div class="flickr_badge"><h3>%s</h3><script src="http://www.flickr.com/badge_code_v2.gne?%s" type="text/javascript"></script></div>', $content, http_build_query($query_atts));
}

add_shortcode('flickrbadge', 'flickr_badge_shortcode');

And would be called from the post content with opening and closing shortcode tags:

[flickrbadge count="4" layout="h" display="latest" size="t" source="all_tag" tag="fish"]Here’s the latest fish[/flickrbadge]

Caution!
Best to avoid camelCase notation in the attributes – the regex that the content is passed through to locate shortcodes is case-insensitive.
Always remember to use return in the handler function and not echo (in this example sprintf, not printf). It’ll appear on the page – but not in the right place…

WordPress shortcodes are relatively simple in concept, but can be a bit fiddly in practice, keeping track of the default parameters and the use of shortcode_atts() just needs a bit of thinking about sometimes…

It’s really easy to get really mixed up when trying to program with date functions – lots to keep track of, calendars, timezones, daylight saving, weird months that have different numbers of days in them…

Here’s a quick rundown on the main PHP functions involved.

1. checkdate()

bool checkdate ( int $month , int $day , int $year )

Does just what it says, for the Gregorian calendar, and it’s been around since PHP4 – a very quick way to ensure that the programming isn’t coming up with any silly results. Always useful!

2.. date() and gmdate()

From a given UNIX timestamp, date() tells you what time would be in your server timezone and gmdate() tells you what GMT it would be (or UTC, the same thing…). It is important to get the hang of the consequences of this and one way of figuring it out is to bear in mind the date() format character “Z” – the timezone offset in seconds, positive or negative.

No matter what the timezone is set to, these 2 expressions will produce the same result…

<?php
	date_default_timezone_set('America/Montreal');

	echo date("Y/m/d H:i:s",(time()));
	echo gmdate("Y/m/d H:i:s",(time()+ date("Z")));

?>

3. strtotime()

Takes a string and should return a Unix timestamp.

It does say string in “US English date format” – which means that for strtotime (“04/06/2010″) is April 6th, and not the 4th of June. (Probably no need to get into a discussion about the relative logic of the two systems here).

strtotime has a pretty decent understanding of language – so you can do relative times:

strtotime('next Monday');
strtotime('+1 years');
strtotime('first day next month');
strtotime('2010-02 last day');

All return what you’d expect, based on the datetime the function’s run…

4. mktime()

Good for catching “overflows”.

echo date("M-d-Y", mktime(0, 0, 0, 12, 32, 2009)) // => Jan-01-2010
echo date("M-d-Y", mktime(0, 0, 0, 15, 31, 2009)) // => Mar-31-2010

Like strtotime, mktime doesn’t go in unit magnitude order – it’s hours, minutes, seconds, months, days, years…. why? because that’s the decision that was made…

Find a birth day with mktime:-

	$my_birthdate = mktime(0,0,0,5,12,72);
	print date("l", $my_birthdate);
	//gives:   Friday

A Few More Calendar Tricks

Current age

<?php  echo floor(abs(strtotime('Y') - strtotime('02/22/1968'))/31536000);  ?>

Easter date

<?php echo date("M-d-Y", easter_date(2010));   ?>     // Apr-04-2010

Datetime constants
PHP 5.1 and later, via the DateTime class, offers a few shorthand formatting strings.

<?php echo date(DATE_RSS); ?>
//gives something like: Thu, 21 Feb 2010 09:35:44 -0800

The defined strings are here – also good for cookies.

Daylight Saving Problems
One way of cutting out possible problems with daylight saving time differences across timezones is to work in UTC, using expressions like these (and then revert back to a local timezone at the end if necessary).

date_default_timezone_set('UTC');

$date_utc = strtotime($date. " UTC");

Expressivo (Center) is a free WordPress theme – based on Expressivo – a three-column layout, but with the blog post content centered. It’s got the same feature list – a jQuery dropdown pages menu, Cufon embedded fonts for post titles, a custom header image and threaded and paged comments.

Version 1.1 has been tested on Firefox 3, Google Chrome, Internet Explorer 6 & 7 and Opera 9.

Features

• Add your own header image or logo
• jQuery dropdown menu for pages – exclude and configure the item order
• Cufon Embedded fonts
• Custom link and hover colors

Demo: Expressivo (Center) demonstration

Download: Expressivo (Center) WordPress Theme v1.1 – expressivo-center.zip Compatible with WP > version 2.8

This theme is released under the terms of the GPL licence v2.

Our free themes are supplied “as is” – sorry, but we don’t have the resources to offer support for email enquiries or comments about individual installation/customisation.

Mistral is a free WordPress theme – a two-column layout, with a righthand sidebar. Plus a static pages menu, Cufon embedded fonts for widget headings, a replaceable logo area and paged- and threaded- comments.

Version 1.1 has been tested on Firefox 3, Internet Explorer 6 & 7, Google Chrome and Opera 9.

Features

• Replace blog info header with your own logo / design
• Cufon embedded fonts for widget headings
• Customized link and hover colors

Demo: Mistral demonstration

Download: Mistral WordPress Theme v1.1 – mistral.zip Compatible with WP > version 2.9

This theme is released under the terms of the GPL licence, v2.

Our free themes are supplied “as is” – sorry, but we don’t have the resources to offer support for email enquiries or comments about individual installation/customisation.

You need a cron job in your WordPress blog – something run to a schedule, hourly, daily… Instead of fixing up a crontab and using wget or lynx, you can use WordPress’s internal version of the cron job.

This isn’t a true cron job, with a crontab text file sitting on the server – it’s known as a pseudo-cron. Since a script can’t launch itself, it makes use of a visitor, human or maybe robot, launching it by requesting a page. So the job actually runs at the first launch after the scheduled time, not necessarily at the scheduled time to the exact second.

wp_schedule_event()

The most convenient way of using WP-Cron is to wrap it all up in a plugin – so that the scheduling can be done just the once by including it in the plugin activation function.

register_activation_hook(__FILE__, 'my_activation');
add_action('my_hourly_event', 'do_this_hourly');
register_deactivation_hook(__FILE__, 'my_deactivation'); 

function my_activation() {
wp_schedule_event(time(), 'hourly', 'my_hourly_event');
}

function my_deactivation() {
	wp_clear_scheduled_hook('my_hourly_event');
}

function do_this_hourly() {
	// do something here every hour
}

The PHP time() used as an argument indicates “as of now” – so if the plugin is activated at 11:23, an hourly event is going to run at xx:23 from now onwards.

If your code is in for example functions.php and is executed every time the script is executed, you don’t want to keep scheduling the same event. Something like this prevents the problem:-

if (empty(wp_next_scheduled('my_event')))
		wp_schedule_event(time(), 'daily', 'my_event');

WP-Cron Hourly, Recurrence Intervals

Only hourly, daily and twicedaily are available immediately – but there’s a trick to getting more and that’s to tap into the cron_schedules filter and add a key to the schedules array.

add_filter('cron_schedules', 'my_add_weekly');

function my_add_weekly( $schedules ) {
	$schedules['weekly'] = array(
		'interval' => 604800, //that's how many seconds in a week, for the unix timestamp
		'display' => __('Once Weekly')
	);
	return $schedules;
}