display author name in widget wordpress

widget show author

<?php if(is_home() || is_single()){ 
           
           echo get_the_author($post->post_author);  
           echo ' 
<style>
.linklien{
border: 2px solid #444 ; 
background-color:blue;
}
</style>
<p class="linklien">
<a href="localhost/wptest/messages/sentbox/">
Envoyez un message</a></p>' ;
 } ?> 
 this working with plugin code php widget for wordpress
 //// 
 
 
 
<div class="about-author-info">                                
        <h3>A propos de l'auteur <small>Voir tous les cours par <?php the_author_posts_link(); ?></small></h3>
    </div>
<div class="about-author-description">
        <?php the_author_meta("description"); ?>
<a href="mailto:<?php the_author_email(); ?>">Contacter l'auteur de ce cours</a>

    </div>///// 3rd solution 
    
    
    <div class="about-author-info">                                
        <h3>A propos de l'auteur <small>Voir tous les cours par <?php the_author_posts_link(); ?></small></h3>
    </div>
<div class="about-author-description">
        <?php the_author_meta("description"); ?><br>
</div>
<br>
<div class="Sendemail">
<form method="POST">
<TEXTAREA name="Message" placeholder="contacter l'enseignant de ce cours" cols="20" rows="5"></TEXTAREA> 
<br>
<Input type="SUBMIT" name="submit" value="Envoyer"  align="center" style="margin-top:12px;"></input>
</div>
<?php 
$headers  = 'MIME-Version: 1.0' . "\r\n";
$headers .= 'From: contact.schoolmania.net  ' . "\r\n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";
    $Message= $_POST['Message'];
    $to =the_author_email();
    $subject = 'Email ';
    $body = "message d'un etudiant";
if ($_POST['submit']) {
    if(mail($to, $subject, $Message.$body, $headers)) { 
        echo '<p>Merci pour votre email!</p>';
    } else { 
        echo '<p>Oops! erreur , verifiez encore les champs .</p>'; 
    }}?>

add_filter( 'comments_open', 'my_comments_open', 10, 2 );

function my_comments_open( $open, $post_id ) {

$post = get_post( $post_id );

if ( 'page' == $post->post_type )
	$open = false;

return $open;

}