I need to change the last modified date and time of all of my blog’s posts in WordPress. So far i have….

add_action( 'wp', 'asd' );
function asd()
{
    $post_list = get_posts( array(
    'post_per_page'    => '-1'
    ) );

    foreach ( $post_list as $post ) {
   // $posts[] += $post->ID;

    $postID = $post->ID;
    $datetime = date( 'Y-m-d H:i:s', current_time( 'timestamp', 0 ) );  
    echo $postID . ' ||| ' . $datetime . '<br>';

global $wpdb;
$wpdb->query( "UPDATE `$wpdb->posts` SET `post_modified` = '" . $datetime . "'  WHERE ID = " . $postID);
}
}

I get no errors or whatsoever. I am using “echo” for debugging purposes. I have two problems.

1. I have 6 posts and i get only 5
2. It seems that no update is happening in the database, for the last modified field

Any help would be appreciated.

Read more here: Change WordPress Posts’ last_modified date and time with WP Query