WordPress meta box with image uploader

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functions.php
------------------------------------------------------------

<?php
$prefix = 'abc-';

$meta_box = array(

'id' => 'my-meta-box',
'title' => 'My Meta Box',
'pages' => array('post'),
'context' => 'normal',
'priority' => 'high',
'fields' => array(

array(
'name' => 'Book cover',
'desc' => 'Add book cover image',
'id' => 'book-cover',
'type' => 'text',
),

array(
'name' => '',
'desc' => '',
'id' => 'book-cover-button',
'type' => 'button',
'std' => 'Browse'
)

)
);

foreach ($meta_boxes as $meta_box) {
$my_box = new My_meta_box($meta_box);
}

class My_meta_box {

protected $_meta_box;

// create meta box based on given data
function __construct($meta_box) {
if (!is_admin()) return;

$this->_meta_box = $meta_box;

// fix upload bug: http://www.hashbangcode.com/blog/add-enctype-wordpress-post-and-page-forms-471.html
$current_page = substr(strrchr($_SERVER['PHP_SELF'], '/'), 1, -4);
if ($current_page == 'page' || $current_page == 'page-new' || $current_page == 'post' || $current_page == 'post-new') {
add_action('admin_head', array(&$this, 'add_post_enctype'));
}

add_action('admin_menu', array(&$this, 'add'));

add_action('save_post', array(&$this, 'save'));
}

function add_post_enctype() {
echo '
<script type="text/javascript">
jQuery(document).ready(function(){
jQuery("#post").attr("enctype", "multipart/form-data");
jQuery("#post").attr("encoding", "multipart/form-data");
});
</script>';
}

/// Add meta box for multiple post types
function add() {
foreach ($this->_meta_box['pages'] as $page) {
add_meta_box($this->_meta_box['id'], $this->_meta_box['title'], array(&$this, 'show'), $page, $this->_meta_box['context'], $this->_meta_box['priority']);
}
}

// Callback function to show fields in meta box
function show() {
global $post;

// Use nonce for verification
echo '<input type="hidden" name="mytheme_meta_box_nonce" value="', wp_create_nonce(basename(__FILE__)), '" />';

echo '<table class="form-table">';

foreach ($this->_meta_box['fields'] as $field) {
// get current post meta data
$meta = get_post_meta($post->ID, $field['id'], true);

echo '<tr>',
'<th style="width:20%"><label for="', $field['id'], '">', $field['name'], '</label></th>',
'<td>';
switch ($field['type']) {
case 'text':
echo '<input type="text" name="', $field['id'], '" id="', $field['id'], '" value="', $meta ? $meta : $field['std'], '" size="30" style="width:97%" />',
'<br />', $field['desc'];
break;
case 'textarea':
echo '<textarea name="', $field['id'], '" id="', $field['id'], '" cols="60" rows="4" style="width:97%">', $meta ? $meta : $field['std'], '</textarea>',
'<br />', $field['desc'];
break;
case 'select':
echo '<select name="', $field['id'], '" id="', $field['id'], '">';
foreach ($field['options'] as $option) {
echo '<option', $meta == $option ? ' selected="selected"' : '', '>', $option, '</option>';
}
echo '</select>';
break;
case 'radio':
foreach ($field['options'] as $option) {
echo '<input type="radio" name="', $field['id'], '" value="', $option['value'], '"', $meta == $option['value'] ? ' checked="checked"' : '', ' />', $option['name'];
}
break;
case 'checkbox':
echo '<input type="checkbox" name="', $field['id'], '" id="', $field['id'], '"', $meta ? ' checked="checked"' : '', ' />';
break;
case 'file':
echo $meta ? "$meta<br />" : '', '<input type="file" name="', $field['id'], '" id="', $field['id'], '" />',
'<br />', $field['desc'];
break;

case 'button':
echo '<input type="button" name="', $field['id'], '" id="', $field['id'], '"value="', $meta ? $meta : $field['std'], '" />';
break;

case 'image':
echo $meta ? "<img src=\"$meta\" width=\"150\" height=\"150\" /><br />$meta<br />" : '', '<input type="file" name="', $field['id'], '" id="', $field['id'], '" />',
'<br />', $field['desc'];
break;
}
echo '<td>',
'</tr>';
}

echo '</table>';
}

// Save data from meta box
function save($post_id) {
// verify nonce
if (!wp_verify_nonce($_POST['mytheme_meta_box_nonce'], basename(__FILE__))) {
return $post_id;
}

// check autosave
if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
return $post_id;
}

// check permissions
if ('page' == $_POST['post_type']) {
if (!current_user_can('edit_page', $post_id)) {
return $post_id;
}
} elseif (!current_user_can('edit_post', $post_id)) {
return $post_id;
}

foreach ($this->_meta_box['fields'] as $field) {
$name = $field['id'];

$old = get_post_meta($post_id, $name, true);
$new = $_POST[$field['id']];

if ($field['type'] == 'file' || $field['type'] == 'image') {
$file = wp_handle_upload($_FILES[$name], array('test_form' => false));
$new = $file['url'];
}

if ($new && $new != $old) {
update_post_meta($post_id, $name, $new);
} elseif ('' == $new && $old && $field['type'] != 'file' && $field['type'] != 'image') {
delete_post_meta($post_id, $name, $old);
}
}
}
}

function my_admin_scripts() {
wp_enqueue_script('media-upload');
wp_enqueue_script('thickbox');
wp_register_script('my-upload', get_bloginfo('template_url') . '/scripts/uploader.js', array('jquery','media-upload','thickbox'));
wp_enqueue_script('my-upload');
}
function my_admin_styles() {
wp_enqueue_style('thickbox');
}
add_action('admin_print_scripts', 'my_admin_scripts');
add_action('admin_print_styles', 'my_admin_styles');

?>


------------------------------------------------------------
js file
-------------------------------------------------------------

jQuery(document).ready(function() {
jQuery('#book-cover-button').click(function() {
window.send_to_editor = function(html) {
imgurl = jQuery('img',html).attr('src');
jQuery('#book-cover').val(imgurl);
tb_remove();
}
tb_show('', 'media-upload.php?post_id=1&amp;type=image&amp;TB_iframe=true');
return false;
});
});