Checkboxes & Ajax

gistfile1.php

<?php
//Plugin Name: Checkboxes & Ajax
//Description: In re to http://wordpress.stackexchange.com/questions/61390/edit-post-meta-with-checkboxes-on-front-end

//add our test checkboxes
add_filter( 'the_content', 'cba_add_checkboxes'); 
function cba_add_checkboxes( $c ) {

	$first = get_post_meta( get_the_ID(), 'first_item_key', true );
	$second = get_post_meta( get_the_ID(), 'second_item_key', true );

	$c .= '<p class="cba"><input type="checkbox"  name="test_value_1" '. checked( $first, 'true', false ) .' /><br />
	<input type="checkbox" name="test_value_2" '. checked( $second, 'true', false ) .' />
	<input type="hidden" name="post_id" value="'. get_the_ID() .'" /><br /><span class="response"></span></p>';

	return $c;
}

//enqueue our scripts - this is the lazy way :(
//we should be properly enqueuing and localizing the scripts
add_action('wp_footer', 'cba_script');
function cba_script() {
	wp_enqueue_script('jquery');
	?><script>
	jQuery(document).ready( function($) {
		var ajaxurl = '<?php echo admin_url( 'admin-ajax.php' ); ?>';
		var spinner = '<?php echo admin_url( 'images/wpspin_light.gif' ); ?>';
		$('.cba input').click( function() {
            var p = $(this).parent('p');
            p.find('.response').html('<img src="'+spinner+'" />');
            $.post(ajaxurl, {
                'action': 'update_custom_fields',
                'post_id': p.find('input[name="post_id"]').val(),
                'first_item': p.find('input[name="test_value_1"]').is(':checked'),
                'second_item': p.find('input[name="test_value_2"]').is(':checked')
            }, function( response ) {

                p.find('.response').html(response);

            }, 'text');
		});
	});
	</script><?php
}

//hook into the ajax api
add_action( 'wp_ajax_update_custom_fields', 'cba_update_custom_fields' );//for logged-in users
add_action( 'wp_ajax_nopriv_update_custom_fields', 'cba_update_custom_fields' );//for logged-out users
function cba_update_custom_fields() {
    $post_id = $_POST[ 'post_id' ];
    $first_item = $_POST[ 'first_item' ];
    $second_item = $_POST[ 'second_item' ];

    update_post_meta( $post_id, 'first_item_key', $first_item );
    update_post_meta( $post_id, 'second_item_key', $second_item );

    //this message is sent back and displayed as the confirmation message
    //we should probably also have an error message in here
    die('Updated');
}