PHP

How to add custom button in wordpress admin section

add_action( 'manage_post_type_posts_custom_column' , 'my_custom_column', 10, 2 );
function my_custom_column( $column, $post_id ) {
    $my_column_name='NAME-OF-THE-COLUMN';
    switch ( $column ) {
        case $my_column_name:
            echo '<button>My Button</button>';
            break;
    }
}

wordpress add button to admin bar

add_action('admin_bar_menu', 'add_item', 100);

function add_item( $admin_bar ){
  global $pagenow;
  $admin_bar->add_menu( array( 'id'=>'download_counter','title'=>'PDF's Downloaded Today - 1000' ) );
}