WP User Information

gistfile1.php

<?php
    $current_user = wp_get_current_user();
    /**
     * @example Safe usage: $current_user = wp_get_current_user();
     * if ( !($current_user instanceof WP_User) )
     *     return;
     */
    echo 'Username: ' . $current_user->user_login . '<br />';
    echo 'User email: ' . $current_user->user_email . '<br />';
    echo 'User first name: ' . $current_user->user_firstname . '<br />';
    echo 'User last name: ' . $current_user->user_lastname . '<br />';
    echo 'User display name: ' . $current_user->display_name . '<br />';
    echo 'User ID: ' . $current_user->ID . '<br />';
?>

/**--------------------------------------------------------------------*/

  <?php
  $current_user = wp_get_current_user();
  if ( 0 == $current_user->ID ) {
      // Not logged in.
  } else {
      // Logged in.
  }
  ?>