Delete a custom post function value

Question

I'm having an issue with custom functions at the moment, once a value has been added to the database I can not delete the value, what's the best way to solve this?

Basically I've created a custom post type for a games database, when adding a game there are several custom post functions; game developer, publisher, review score and a review URL, now if I enter a test URL it will save that but when I try to delete it, it still appears and wont save the deleted value.

Here is the code I'm using:

<?php
function display_games_database_meta_box( $games_database ) {
// Retrieve information from the game
$game_publisher = esc_html( get_post_meta( $games_database->ID, 'game_publisher', true     ) );
$game_developer = esc_html( get_post_meta( $games_database->ID, 'game_developer', true ) );
$game_rating = intval( get_post_meta( $games_database->ID, 'game_rating', true ) );
$game_review_link = esc_html( get_post_meta( $games_database->ID, 'game_review_link', true ) );
$game_release = esc_html( get_post_meta( $games_database->ID, 'game_release', true ) );
?>
<table>
    <tr>
        <td style="width: 100%">Game Publisher</td>
        <td><input type="text" size="80" name="games_database_game_publisher" value="<?    php echo $game_publisher; ?>" /></td>
    </tr>
    <tr>
        <td style="width: 100%">Game Developer</td>
        <td><input type="text" size="80" name="games_database_game_developer" value="<?php echo $game_developer; ?>" /></td>
    </tr>
    <tr>
        <td style="width: 150px">Game Rating</td>
        <td>
            <select style="width: 100px" name="games_database_rating">
            <option value="No Score">No Score</option>
            <?php
            // Generate all items of drop-down list
            for ( $rating = 10; $rating >= 1; $rating -- ) {
            ?>
                <option value="<?php echo $rating; ?>" <?php echo selected( $rating, $game_rating ); ?>>
                <?php echo $rating; ?>/10<?php } ?>

            </select>
        </td>
    </tr>
    <tr>
        <td style="width: 100%">Review Link (Use the full URL)</td>
        <td><input type="text" size="80" name="games_database_review_link" value="<?php echo $game_review_link; ?>" /></td>
    </tr>        
    <tr>
        <td style="width: 100%">Game Release Date (Format: June 26th 2013)</td>
        <td><input type="text" size="80" name="games_database_game_release" value="<?    php echo $game_release; ?>" /></td>
    </tr>
</table>
<?php
}
?>
<?php
// Adds and saves the game to the database
add_action( 'save_post', 'add_games_database_fields', 10, 4 );
function add_games_database_fields( $games_database_id, $games_database ) {
// Check post type for games
if ( $games_database->post_type == 'games_database' ) {
    // Store data in post meta table if present in post data
    if ( isset( $_POST['games_database_game_publisher'] ) && $_POST['games_database_game_publisher'] != '' ) {
        update_post_meta( $games_database_id, 'game_publisher', $_POST['games_database_game_publisher'] );
    }
    if ( isset( $_POST['games_database_game_developer'] ) && $_POST['games_database_game_developer'] != '' ) {
        update_post_meta( $games_database_id, 'game_developer', $_POST['games_database_game_developer'] );
    }
    if ( isset( $_POST['games_database_rating'] ) && $_POST['games_database_rating'] != '' ) {
        update_post_meta( $games_database_id, 'game_rating', $_POST['games_database_rating'] );
    }
    if ( isset( $_POST['games_database_review_link'] ) && $_POST['games_database_review_link'] != '' ) {
        update_post_meta( $games_database_id, 'game_review_link', $_POST['games_database_review_link'] );
    }
    if ( isset( $_POST['games_database_game_release'] ) && $_POST['games_database_game_release'] != '' ) {
        update_post_meta( $games_database_id, 'game_release', $_POST['games_database_game_release'] );
    }
}
}

Can you see where I'm going wrong?

Answer 1

Your function is checking to see if anything "is set" before proceeding to update, and also that it isn't an empty string. Remove the "if" portions of your update statements, or better yet, put an "else" after to delete post meta if it is empty.

Example:

if ( isset( $_POST['games_database_game_release'] ) && $_POST['games_database_game_release'] != '' ) {
    update_post_meta( $games_database_id, 'game_release', $_POST['games_database_game_release'] );
} else {
    delete_post_meta( $games_database_id, 'game_release');
}