I am working on a code through which I can send emails to the user when his/her comments get approved. then I get to know about comment_post. but it is not working.

comment_post is working for the condition in which user adds a new comment it sends the mail but not when the comment get approved..

#Means ($comment_approved === 1) is not working. here is my current and same code as I found on the internet -

function show_message_function( $comment_ID, $comment_approved ) {
if ( $comment_approved === 1 ) {  // $comment_approved === 0 is working when to send email whenever user insert a new comment
    $message = The Message I'd like to send back to the commenter; 
     $comment=get_comment($comment_ID);
     $mailTo = $comment-comment_author_email ;        
    $subject = sprintf( 'Your comment is approved, comment by: %s', $comment-comment_author.$comment-comment_author_email );
$headers = array('Content-Type: text/html; charset=UTF-8');

     wp_mail($mailTo, $subject, $message, $headers);
        }  
}
add_action( 'comment_post', 'show_message_function', 10, 2 );

What I have tried

tried using wp_get_comment_status()

function show_message_function( $comment_ID, $comment_approved ) { 
$status = wp_get_comment_status( $comment_id ); 
if ( 'approved' === $status ) {
$message = The Message I'd like to send back to the commenter; $comment=get_comment($comment_ID); 
$mailTo = $comment-comment_author_email ;
$subject = sprintf( 'New Comment by: %s', $comment-comment_author.$comment-comment_author_email ); 
$headers = array('Content-Type: text/html; charset=UTF-8');
wp_mail($mailTo, $subject, $message, $headers);
     }  
} 
add_action( 'comment_post', 'show_message_function', 10, 2 );

tried replacing '===' with '=' '==' (single and double equals symbols) [when added single equal symbol ($comment_approved = 1), it sends mail when user enteres/submits a comment but not on approval]

function show_message_function( $comment_ID, $comment_approved ) { if ( $comment_approved = 1 ) { // tried double equal symbols also.

     $message = The Message I'd like to send back to the commenter; 
      $comment=get_comment($comment_ID);
      $mailTo = $comment-comment_author_email ;        
     $subject = sprintf( 'Your comment is approved, comment by: %s', $comment-comment_author.$comment-comment_author_email );
 $headers = array('Content-Type: text/html; charset=UTF-8');

      wp_mail($mailTo, $subject, $message, $headers);
         }  
 }
 add_action( 'comment_post', 'show_message_function', 10, 2 );

tried to disable all plugins (tried wp_debug and show_errors also)

tried to debug wp_mail by 'wp mail tester' and 'email log' plugins (wp_mail is working because the above code is able to send mail when comment is inserted but not when approved!)