If Meta Checkbox is checked, do something?

Question

I created a custom checkbox that when I check, I wish it to display slightly different content (specially special css styling). For some reason it is not functioning properly.

In my functions:

add_action( 'add_meta_boxes', 'add_special_checkbox' );
function add_special_checkbox()
{
    add_meta_box( 'special-checkbox', 'Special Box', 'special_checkbox_func', 'post', 'side', 'high' );
}

function special_checkbox_func( $post )
{
    $values = get_post_custom( $post->ID );
    $check = isset( $values['special_box_check'] ) ? esc_attr( $values['special_box_check'][0] ) : '';
    wp_nonce_field( 'my_special_box_nonce', 'special_box_nonce' );
    ?>
    <p>
        <input type="checkbox" name="special_box_check" id="special_box_check" <?php checked( $check, 'on' ); ?> />
        <label for="special_box_check">Is this post 'special?'</label>
    </p>
    <?php   
}


add_action( 'save_post', 'special_checkbox_save' );
function special_checkbox_save( $post_id )
{
    // Bail if we're doing an auto save
    if( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) return;

    // if our nonce isn't there, or we can't verify it, bail
    if( !isset( $_POST['special_box_nonce'] ) || !wp_verify_nonce( $_POST['special_box_nonce'], 'my_special_box_nonce' ) ) return;

    // if our current user can't edit this post, bail
    if( !current_user_can( 'edit_post' ) ) return;

    // now we can actually save the data
    $allowed = array( 
        'a' => array( // on allow a tags
            'href' => array() // and those anchords can only have href attribute
        )
    );

    // This is purely my personal preference for saving checkboxes
    $chk = ( isset( $_POST['special_box_check'] ) && $_POST['special_box_check'] ) ? 'on' : 'off';
    update_post_meta( $post_id, 'special_box_check', $chk );
}
?>

In my loop:

<?php if (get_post_meta($post->ID, 'special_box_check', true)) { ?>
//add special styling
<? } else { ?>
//dont add special styling
<?php } ?>

When I save some posts, they have the special styling even though I did not check the box for them. And when I uncheck a box, I'd like the special styling to go away, but it is not when the box is unchecked.

I am sure I am doing something wrong here. Thanks in advance.

Answer 1

You're setting a value whether it's checked or not with this line:

$chk = ( isset( $_POST['special_box_check'] ) && $_POST['special_box_check'] ) ? 'on' : 'off';

The value is going to be either on or off, so your if condition is always true, since it always has a value.

You could change it to save only if it's checked, or delete it if it's not. That way your condition will work, and you won't have extra meta entries just to save the off state.

if ( isset( $_POST['special_box_check'] ) && $_POST['special_box_check'] ) {
    add_post_meta( $post_id, 'special_box_check', 'on', true );
} else {
    delete_post_meta( $post_id, 'special_box_check' );
}

Answer 2

Code is perfectly alright nothing to delete just you need to have a conditional in place

// check against the custom field has a value
if ( get_post_meta($post->ID, 'special_box_check', true) == 'on' ) ) {
   $class = 'highlight';
} else{
   $class = 'normal';
}

Place $class variable in your div wrapper. Your style will appears like this:

.highlight{ color:#FF0000; }
.normal{ color:#000; }