Problem for recover and save metaboxes

Question

Your code:

add_action('admin_menu', 'reaction_buttons_meta_box2');

Use 'add_meta_boxes' to add meta boxes. It fires in the wp-admin/edit-form-advanced.php file and passes the $post object. The 'admin_menu' action fires much more often.

add_action( 'add_meta_boxes', 'reaction_buttons_meta_box2' );

Your code:

function reaction_buttons_meta2()
{
global $post;
echo $_POST['reaction_buttons_off2'];

There is nothing in $_POST when the the edit page loads. You can test this with wp_die().

add_action( 'add_meta_boxes', 'reaction_buttons_meta_box2' );

function reaction_buttons_meta_box2() {
    add_meta_box( 'reaction_buttons2', 'Reaction Buttons', 'reaction_buttons_meta2', 'post', 'side' );
    add_meta_box( 'reaction_buttons2', 'Reaction Buttons', 'reaction_buttons_meta2', 'page', 'side' );
}

function reaction_buttons_meta2() {
    wp_die( '<pre>' . var_export( $_POST, true ) . '</pre>' );
}

In the meta box you should see this:

array(
)

Which means nothing is in $_POST.

Your code:

update_post_meta($post->ID, 'reaction_buttons_off2', $_POST['reaction_buttons_off2']);

reaction_buttons_meta_box2() is not run during post / page save. To add a function on save use this:

add_action( 'add_meta_boxes', 'reaction_buttons_meta_box2' );
add_action( 'save_post', 'wpse_47828_reaction_buttons_meta_box2_save' );

function wpse_47828_reaction_buttons_meta_box2_save() {
    wp_die( '<pre>' . var_export( $_POST['reaction_buttons_off2'], true ) . '</pre>' );
}

function reaction_buttons_meta2() {
    printf( '<input type="text" id="%1$s" name="%1$s" value="%2$s" />', 'reaction_buttons_off2', 12 );
}

function reaction_buttons_meta_box2() {
    add_meta_box( 'reaction_buttons2', 'Reaction Buttons', 'reaction_buttons_meta2', 'post', 'side' );
    add_meta_box( 'reaction_buttons2', 'Reaction Buttons', 'reaction_buttons_meta2', 'page', 'side' );
}

Refresh the editor page and Update the post. The web page should produce an error with '12' in it. The value added in the printf line above.

Your code:

$meta=get_post_meta($post->ID, $field['reaction_buttons_off2'], true);

This code used a variable named $field which has never been defined. It should produce a PHP error.

Your code:

<input type="text" id="reaction_buttons_off2" name="reaction_buttons_off2" value="<?php echo $meta[reaction_buttons_off2][0]; ?>">

This code uses an array key named reaction_buttons_off2 without quotes. Since $field didn’t exist in the line above, $meta has nothing in it and the corrected code $meta['reaction_buttons_off2'][0] should produce a PHP missing index warning.

reaction_buttons_meta2() should probably look like this:

function reaction_buttons_meta2( $post ) {

    $field_name="reaction_buttons_off2";

    if ( get_post_meta( $post->ID, $field_name, true ) )
        $reaction_buttons_off2 = get_post_meta( $post->ID, $field_name, true );
    else
        $reaction_buttons_off2 = '';

    printf( '<input type="text" id="%1$s" name="%1$s" value="%2$s" />', $field_name, $reaction_buttons_off2 );
}

Saving the data requires some tests:

function wpse_47828_reaction_buttons_meta_box2_save( $post_id ) {

    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
        return;

    if ( current_user_can( 'edit_post', $post_id ) || current_user_can( 'edit_pages', $post_id ) ) {

        $field_name="_reaction_buttons_off2";

        if ( isset( $_POST[$field_name] ) )
            update_post_meta( $post_id, $field_name, $_POST[$field_name] );
    }
}

The field name, reaction_buttons_off2 will show up as a custom field and can be edited there as well. If you wish to avoid that add an underscore to the beginning of the field name in both the wpse_47828_reaction_buttons_meta_box2_save() and in reaction_buttons_meta2().

$field_name="_reaction_buttons_off2";

Putting it all together:

add_action( 'add_meta_boxes', 'reaction_buttons_meta_box2' );
add_action( 'save_post', 'wpse_47828_reaction_buttons_meta_box2_save' );

function reaction_buttons_meta_box2() {
    add_meta_box( 'reaction_buttons2', 'Reaction Buttons', 'reaction_buttons_meta2', 'post', 'side' );
    add_meta_box( 'reaction_buttons2', 'Reaction Buttons', 'reaction_buttons_meta2', 'page', 'side' );
}

function reaction_buttons_meta2( $post ) {

    $field_name="_reaction_buttons_off2";

    if ( get_post_meta( $post->ID, $field_name, true ) )
        $reaction_buttons_off2 = get_post_meta( $post->ID, $field_name, true );
    else
        $reaction_buttons_off2 = '';

    printf( '<input type="text" id="%1$s" name="%1$s" value="%2$s" />', $field_name, $reaction_buttons_off2 );
}

function wpse_47828_reaction_buttons_meta_box2_save( $post_id ) {

    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
        return;

    if ( current_user_can( 'edit_post', $post_id ) || current_user_can( 'edit_pages', $post_id ) ) {

        $field_name="_reaction_buttons_off2";

        if ( isset( $_POST[$field_name] ) )
            update_post_meta( $post_id, $field_name, $_POST[$field_name] );
    }
}

Note: You should add some validation to the field during save and it may be a good idea to also add a nonce to check that this form really came from WordPress admin. I don’t know if current_user_can() will be secure enough.

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