Render the metabox

<?php
//Diese Funktion rendert die Metabox
function us_meta_box_url_render( $post ){
    ?>
    <?php
        wp_nonce_field( 'save-url', 'us_nonce' );
    ?>
    <p>
        <label for="redirect-url">URL:</label><br />
        <input type="text" id="redirect-url" value="<?php
            echo esc_attr( urldecode( get_post_meta( $post->ID, 'url', true ) ) );
        ?>" name="url" />
    </p>
    <?php
}
?>