Wordpress temporary session to save any message?

If you need to save any error OR success message on wordpress function.php file OR any other file then please follow below steps:

Here I explain with one success message save on function file and display on home page:

function.php

<?php
function myTempFun() {
   if(!session_id()) {
       session_start();
   }
   $_SESSION['my_session_name'] = 'Write here any message';
}
?>

home page template.php

if ( array_key_exists( 'my_session_name', $_SESSION ) ) {?>
    <p><?php echo $_SESSION['my_session_name']; ?></p>
<?php
    unset( $_SESSION['my_session_name'] );
}

After session display also unset that , So when you refresh page then second time that session not displaying.

Enjoy!