create a custom metabox in wordpress

https://www.dropbox.com/s/76xabzzqqzoeh2c/sample.php?dl=0
//additional info reffer https://developer.wordpress.org/plugins/metadata/creating-custom-meta-boxes/
function create_metabox_from($post)
{
    $data=get_post_meta( $post->ID,"message");//receiving saved data 
   
    ?>

<input type="text" name="message" id="message" class="widefat" value="<?php echo $data[0];?>">


<?php

}
function create_metabox()
{
    $screen=array("Samples");//it is the post which this meta box need to be apperare
    foreach($screen as $key)
    {
        add_meta_box("sample_metabox","message","create_metabox_from",$screen,"");
    }
   
}
add_action("add_meta_boxes","create_metabox");//creating metabox
add_action( 'save_post', 'save_data' );//saving metabox data
function save_data($post_id)
{
   
    if(array_key_exists("message",$_POST))
    {
        update_post_meta($post_id,"message",$_POST['message']);
    }
}