Create Custom MetaBox DASAR

KODE MEMBUAT METABOX di function.php:

function custom_post_metaboxes() {
add_meta_box('ob-post', 'Custom Post', 'custom_post_func', 'post', 'normal', 'high');
}
add_action('admin_menu', 'custom_post_metaboxes');
function custom_post_func(){
global $post;

echo '<input type="hidden" name="custom_post_custom_nonce" id="ob_post_custom_nonce" value="' .
wp_create_nonce( plugin_basename(__FILE__) ) . '" />';

$custom_post_value = get_post_meta($post->ID, 'custom_post_value', true);
?>
<table>
<tbody>
<tr>
<td>Value :</td>
<td><input type="text" name="custom_post_value" value="<?php echo $custom_post_value; ?>"/></td>
</tr>
</tbody>
</table>
<?php
}
function custom_post_func_save($post_id, $post){
if ( !wp_verify_nonce( $_POST['custom_post_custom_nonce'], plugin_basename(__FILE__) )) {
return $post->ID;
}

if ( !current_user_can( 'edit_post', $post->ID ))
return $post->ID;

$custom_post_value['custom_post_value'] = $_POST['custom_post_value'];

foreach ($custom_post_value as $key => $value) {
if( $post->post_type == 'revision' ) return;
if(get_post_meta($post->ID, $key, FALSE)) {
update_post_meta($post->ID, $key, $value);
} else {
add_post_meta($post->ID, $key, $value);
}
if(!$value) delete_post_meta($post->ID, $key);
}
}
add_action('save_post', 'custom_post_func_save', 1, 2);

==========================================

KODE MENAMPILKAN METABOX di single.php
$custom_post_box = get_post_meta(get_the_ID(), "custom_post_value", true);
echo $custom_post_box;