[PHP/Wordpress] Define a default post password with filters and hooks

functions.php

add_filter( 'post_password_required', function( $returned, $post )
{
  //Define here your conditional logic, example filter posts without password from custom post type "photo_gallery"

  if (empty($post->post_password) && $post->post_type=="photo_galery")
	  $post->post_password='Secretpw123';

  //End of conditional logic. Returning true will ask for password, false will display the content.
  require_once ABSPATH . WPINC . '/class-phpass.php';
  $hasher = new PasswordHash( 8, true );
  $hash = wp_unslash( $_COOKIE[ 'wp-postpass_' . COOKIEHASH ] );
  if ( 0 !== strpos( $hash, '$P$B' ) )
        $required = true;
  else
        $required = ! $hasher->CheckPassword( $post->post_password, $hash );
	return $required;
}, 10, 2 );