An authentication filter for your WordPress development environment

auth-filter.php

<?php
/**
* Filters 'authenticate'
* to keep user with id 1 
* logged in without needing
* to enter l/p
*/

add_filter( 'authenticate', 'wwm_authenticate_filter', 10, 1 );

/**
 * The filtering function. If needed, the hook
 * passes a total of 3 paramaters, but in this case
 * only one is needed.
 * @param $user null|WP_User|WP_Error
 * @see wp-includes/pluggable.php wp_authenticate_user
 * 
 */
function wwwm_authenticate_filter( $user ) {
  /**
  * Because somebody is just going to copy & paste
  * this and use it - conditionally check and ONLY
  * auto login user 1 if this is running on 'localhost'
  */
  if ( 127.0.0.1 == $_SERVER['REMOTE_ADDR'] ) {
    $user = new WP_User( 1 );
  }
  
  return $user;
}