Wordpress plugin with AJAX support

hello-world.php

<?php
/*
Plugin Name: Hello World 4
Plugin URI: http://ocaoimh.ie/
Description: A simple hello world plugin
Version: 0.1
Author: Donncha O Caoimh
Author URI: http://ocaoimh.ie/
*/

function hello_world_4_pages() {
	add_options_page('Hello World 4', 'Hello World 4', 'manage_options', 'helloworld4', 'hello_world_4');
}
add_action('admin_menu', 'hello_world_4_pages');


function hello_world_4() {
	$nonce = wp_create_nonce( 'helloworld' );
	?>
<script  type='text/javascript'>
<!--
var count = 0;

function update_hello_world( count ) {
	jQuery.ajax({
		type: "post",url: "admin-ajax.php",data: { action: 'gethello4', count: count, _ajax_nonce: '<?php echo $nonce; ?>' },
		beforeSend: function() {jQuery("#helloworld").fadeOut('fast');}, //fadeIn loading just when link is clicked
		success: function(html){ //so, if data is retrieved, store it in html
			jQuery("#helloworld").html(html); //fadeIn the html inside helloworld div
			jQuery("#helloworld").fadeIn("fast"); //animation
		}
	}); //close jQuery.ajax(
}
// When the document loads do everything inside here ...
jQuery(document).ready(function(){
	jQuery('#random').click(function() { //start function when Random button is clicked
		jQuery.ajax({
			type: "post",url: "admin-ajax.php",data: { action: 'randomcol', _ajax_nonce: '<?php echo $nonce; ?>' },
			beforeSend: function() {jQuery("#loading").fadeIn('fast');}, //fadeIn loading just when link is clicked
			success: function(html){ //so, if data is retrieved, store it in html
				jQuery("#loading").fadeOut('slow');
				jQuery("#colour").val(html); //fadeIn the html inside helloworld div
				jQuery("#helloworld").fadeIn("fast"); //animation
			}
		}); //close jQuery.ajax
		return false;
	})
	jQuery('#save').click(function() { //start function when Random button is clicked
		jQuery.ajax({
			type: "post",url: "admin-ajax.php",data: { action: 'colour', colour: escape( jQuery( '#colour' ).val() ), _ajax_nonce: '<?php echo $nonce; ?>' },
			beforeSend: function() {jQuery("#loading").fadeIn('fast');jQuery("#formstatus").fadeOut("fast");}, //fadeIn loading just when link is clicked
			success: function(html){ //so, if data is retrieved, store it in html
				jQuery("#loading").fadeOut('slow');
				jQuery("#formstatus").html( html ); //show the html inside formstatus div
				jQuery("#formstatus").fadeIn("fast"); //animation
				jQuery("#formstatus").fadeOut(5000); //animation
			}
		}); //close jQuery.ajax
		return false;
	})
})
-->
</script>
<style type='text/css'>
#loading { clear:both; background:url(images/loading.gif) center top no-repeat; text-align:center;padding:33px 0px 0px 0px; font-size:12px;display:none; font-family:Verdana, Arial, Helvetica, sans-serif; }
</style>
<div class="wrap">
<form action='' method='POST' id='helloworld4form'>
<p>Colour: <input type='text' name='colour' id='colour' value='#000000' /></p>
<p><input type='submit' name='action' id='random' value='Random' /> <input type='submit' name='action' id='save' value='Save' /></p>
</form>
<div id='formstatus'></div>
<div id='loading'>LOADING!</div>
</div><?php
}

function save_colour() {
	check_ajax_referer( "helloworld" );
	echo 'Saved colour: ' . urldecode( $_POST[ 'colour' ] );
	die();
}
add_action( 'wp_ajax_colour', 'save_colour' );

function get_randomcol() {
	check_ajax_referer( "helloworld" );
	$col = substr( mt_rand(), 0, 6 );
	echo '#' . $col;
	die();
}
add_action( 'wp_ajax_randomcol', 'get_randomcol' );
?>