function mycnt(){
    global $post;
    ?>
    <div class="my-meta-bx-meh">
        <form action="" method="post">
            <table>
               <h4>download section</h4>
                <tr>
                    <td><label for="">download link 320</label></td>
                    <td></td>
                    <td></td>
                    <td></td>
                    <td><input name="downloadlink" value="<?php if(get_post_meta($post->ID,'downloadlink',true) !=""){ echo get_post_meta($post->ID,'downloadlink',true);} ?>" type="text"/></td>
                </tr>
                <tr>
                    <td><label for="">download link 128</label></td>
                    <td></td>
                    <td></td>
                    <td></td>
                    <td><input name="playlink" value="<?php if(get_post_meta($post->ID,'playlink',true) !=""){ echo get_post_meta($post->ID,'playlink',true);} ?>" type="text"/></td>
                </tr>
            </table>
        </form>
    </div>
<?php

}

function my_func_bx(){
    add_meta_box('mymbxid','music mosije','mycnt','post');
}

function kkmncd(){
    global $post;
    $post_id = $post->ID;

    if(!empty($_POST['downloadlink'])) {
        add_post_meta($post_id, 'downloadlink', addslashes($_POST['downloadlink']), true);
        update_post_meta($post_id, 'downloadlink', addslashes($_POST['downloadlink']), get_post_meta($post->ID, 'downloadlink', true));
    }
    if(empty($_POST['downloadlink'])){
        delete_post_meta($post_id,'downloadlink',get_post_meta($post->ID,'downloadlink',true));
    }

    if(!empty($_POST['playlink'])) {
        add_post_meta($post_id, 'playlink', addslashes($_POST['playlink']), true);
        update_post_meta($post_id, 'playlink', addslashes($_POST['playlink']), get_post_meta($post->ID, 'playlink', true));
    }
    if(empty($_POST['playlink'])){
        delete_post_meta($post_id,'playlink',get_post_meta($post->ID,'playlink',true));
    }
}

add_action('add_meta_boxes','my_func_bx');
add_action('save_post','kkmncd');