gistfile1.php

<?php
if (!class_exists('ApproveFromPreview')){

        class ApproveFromPreview {
                function __construct() {
                    add_filter('the_content',array($this,'add_approve_button'));
                    add_filter('the_content',array($this,'show_approved'));

                    add_action('wp',array($this,'approve_post'));
                }
                public function add_approve_button($content){
                    global $post;
                    if (is_preview() &&  
                        current_user_can( 'edit_post', $post->ID ) &&  
                        current_user_can( 'publish_posts', $post->ID ) &&
                        in_array($post->post_status,array('draft', 'pending'))
                    ){
                        return $this->get_button().$content;
                    }

                    return $content;
                }
                public function show_approved($content){
                    $msg = '';
                    if ( isset( $_GET['msg'] ) ){
                        if( $_GET['msg'] == 'approved' ) 
                            $con =  '<div class="success" style="background: #c9e8f5;padding: 3px;">' . __( '公開されました' ) . '</div>';
                        else
                            $con =  '<div class="error" style="background: #f8c7c7;padding: 3px;">' . __( '記事は下書きのままです' ) . '</div>';
                    }
                    return $con . $content;
                }

                public function get_button(){
                    global $post;
                    return '<a href="'.wp_nonce_url( "?action=AFP&pid=" . $post->ID, 'AFP_NONCE').'" class="button">'.__('この記事を公開する').'</a><br/>';
                }

                public function approve_post(){
                    if (!isset($_REQUEST['_wpnonce']) || 
                        !isset($_REQUEST['pid']) || 
                        !isset( $_REQUEST['action']) || 
                        $_REQUEST['action'] != "AFP" )
                    {
                        return;
                    }

                    $nonce = $_REQUEST['_wpnonce'];
                    if ( !wp_verify_nonce( $nonce, 'AFP_NONCE' ) ) {
                        return; 
                    }
                    $pid = intval($_REQUEST['pid']);
                    if (current_user_can( 'edit_post',$pid ) && current_user_can( 'publish_posts', $pid )){
                        $p = $this->change_post_status($pid,'publish');
                        if ($p > 0){
                            $redirect = add_query_arg( array('msg' => 'approved'), get_permalink($p) );
                            wp_redirect( $redirect );
                            exit;
                        }else{
                            $redirect = add_query_arg( array('msg' => 'not_approved'), get_permalink() );
                            wp_redirect( $redirect );
                            exit;
                        }
                        return;
                    }
                    return;
                }

                public function change_post_status($post_id,$status){
                    $current_post = get_post( $post_id, 'ARRAY_A' );
                    $current_post['post_status'] = $status;
                    return wp_update_post($current_post);
                }
        } 
}
new ApproveFromPreview();

?>