WordPress: conditional script inclusion

MyJS.php

<?php
class MyJS {
	public function __construct() {
		add_action( 'wp_enqueue_scripts', array( &$this, 'addScripts' ) );
	}
	
	
	public function addScripts() {
	
	    // jQuery
	    
		wp_deregister_script( 'jquery' );
		wp_register_script( 'jquery', get_template_directory_uri() . '/js/jquery.js', array(), '2.2', true );
		wp_enqueue_script( 'jquery' );
		
		if( is_single() ) { // singolo post?
			global $post;  // oggetto globale $post
			
			if( has_tag( 'galleria', $post ) ) { // il post ha il tag 'galleria' ?
				wp_register_script( 'fancybox', get_template_directory_uri() . '/js/plugins/fancybox/jquery.fancybox.js', array( 'jquery' ), '2.0', true );
				wp_enqueue_script( 'fancybox' );
				wp_register_style( 'fancybox', get_template_directory_uri() . '/js/plugins/fancybox/jquery.fancybox.css' );
				wp_enqueue_style( 'fancybox' );
			}
		}
		
		// script principale
		
		wp_register_script( 'blog', get_template_directory_uri() . '/js/blog.js', array( 'jquery' ), '1.0', true );
		wp_enqueue_script( 'blog' );
	}
	
}

$myjs = new MyJS();

?>