Cacher is the code snippet organizer for pro developers

<?php
/*
Plugin Name: Instant Gallery
Plugin URI: http://www.heyjohnsexton.com/projects/
Description: Instantly creates a simple image gallery from any images uploaded to a post or page
Author: John Sexton
Version: 1.0
Author URI: http://www.heyjohnsexton.com
*/

/*  Copyright 2012 John Sexton  (email : heyjohnsexton@gmail.com)

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License, version 2, as 
    published by the Free Software Foundation.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

//----------------------------------------------------------------------
// Import Stylesheet
//----------------------------------------------------------------------

function add_stylesheets() {
 
    // change this path to load your own custom stylesheet
	$css_path = WP_PLUGIN_URL . '/instant-gallery/instant-gallery.css';
    
    // registers your stylesheet
    wp_register_style( 'instantGalleryStyles', $css_path );
 
    // loads your stylesheet
    wp_enqueue_style( 'instantGalleryStyles' );
}

// Only add the stylesheet if we are NOT on the admin screen
if (!is_admin()) add_action( 'wp_enqueue_scripts', 'add_stylesheets' );


//---------------------------------------------------------------------------------------
// Enqueue jQuery from Google
//---------------------------------------------------------------------------------------

function enqueue_jquery() {
   
	wp_enqueue_script('jquery');
   
}

// Only add the javascript if we are NOT on the admin screen
add_action("wp_enqueue_scripts", "enqueue_jquery", 11);


//-------------------------------------------------
// Activate Instant Gallery
//-------------------------------------------------

function activate_instant_gallery(){
?>

	<script>

		//	Wrap the jQuery code in the generic function to allow use of 
		//  the $ shortcut in WordPress's no-conflict jQuery environment

		( function ($) {

			$('#ig-thumbs').delegate('img','click', function(){		// When someone clicks on a thumbnail

				$('#ig-hero').attr('src',$(this).attr('src').replace('-150x150',''));	// Replace the Full Sized version of selected image

				$('#ig-thumbs li img').removeClass("selected");				// Remove "selected" class from all thumbnails
				$(this).addClass("selected");								// Add "selected" class to selected thumnail

				$('#ig-title').html($(this).attr('alt'));					// Replace the Title with Title of selected image				
			});


			// Preload all other images in the slideshow so we don't have to wait
			// when we click on them. This also helps avoid awkward transitions 
			// when the description for the new image loads before the new image itself

		})(jQuery);

	</script>
	
<?php
}

// Hook into footer so gallery becomes active after page loads
add_action('wp_footer','activate_instant_gallery');	


//-------------------------------------------------------------
// Instant Image Gallery by John Sexton
//-------------------------------------------------------------

function instant_gallery() {
	
        <!-- Output Buffer -->
	ob_start();
	
	global $post;

	$args = array(
		'post_parent'    => $post->ID,			// For the current post
		'post_type'      => 'attachment',		// Get all post attachments
		'post_mime_type' => 'image',			// Only grab images
		'order'			 => 'ASC',				// List in ascending order
		'orderby'        => 'menu_order',		// List them in their menu order
		'numberposts'    => -1, 				// Show all attachments
		'post_status'    => null,				// For any post status
	);

	// Retrieve the items that match our query; in this case, images attached to the current post.
	$attachments = get_posts($args);
	
		// If any images are attached to the current post, do the following:
		if ($attachments) {	

			// Initialize a counter so we can keep track of which image we are on.
			$count = 0;
			
			// Now we loop through all of the images that we found 
			foreach ($attachments as $attachment) { 
				 		
				// Below here are the main containers and first large image; stuff we will only want to output one time.
				if($count == 0) { ?>
				
					<!-- Whole Gallery container (inludes thumbnails) -->
					<div id="instant-gallery">
						
						<!-- Main Display Area -->
						<div id="ig-main">

								<!-- Set the parameters for the image we are about to display. -->
								<?php $default_attr = array(
										'id' 	=> "ig-hero",
										'alt'   => trim(strip_tags( get_post_meta($attachment_id, '_wp_attachment_image_alt', true) )),
										'title' => trim(strip_tags( $attachment->post_title )),
									);
								?>

								<!-- Display the first image attachment as the large image in the main gallery area -->
								<?php echo wp_get_attachment_image($attachment->ID, 'full', false, $default_attr); ?>

								<!-- Image Title -->
								<p id="ig-title">

								<!-- Display the Title of this image below the main image -->
								<?php echo $attachment->post_title; ?>

								</p>

						<!-- Close the main display area -->
						</div>

						<!-- Open the Thumbnail navigation -->
						<ul id="ig-thumbs">
				
				<!-- End the block of stuff that we only do for the first image  -->
				<?php } ?> 

						<!-- Now, for each of the thumbnail images, label the LI with an ID of the appropriate thumbnail number -->
						<li id="ig-thumb-<?php echo $count+1; ?>">

							<?php if ($count==0) {

									// If this is the first thumbnail, add a class of 'selected' to it so it will be highlighted
									$thumb_attr = array(
										'class' => "thumb selected",
									);

								} else {

									// For all other thumbnails, just add the basic class of 'thumb'
									$thumb_attr = array(
										'class' => "thumb",
									);

								} ?>
					
							<!-- Output a thumbnail-sized version of the image that has the attributes defined above -->
							<?php echo wp_get_attachment_image($attachment->ID, 'thumbnail', false, $thumb_attr); ?>
			
						</li>
				
				<!-- Increment the counter so we can keep track of which thumbnail we are on -->
				<?php $count = $count + 1; } ?>
						
					<!-- Close the thumbnail navigation list -->
					</ul>
	
				<!-- Close the entire Gallery -->
				</div>
			<!-- Return the output -->	
			<?php return ob_get_clean(); ?>
	<?php }

}

// Create the Shortcode
add_shortcode('instant_gallery', 'instant_gallery');

?>