Wordpress custom upload with thumbnail creation

upload-thumnail.php

<?php
 
require_once( ABSPATH . 'wp-admin/includes/file.php' );
require_once( ABSPATH . 'wp-admin/includes/image.php' );
 
if(isset($_FILES['photo']['name']) && !empty($_FILES['photo']['name'])){
    //Upload la photo dans le dossier
    $uploadedfile = $_FILES['photo'];
    $movefile = wp_handle_upload($uploadedfile, array('test_form' => false));
 
    //On sauvegarde la photo dans le média library
    if ($movefile) {
        $wp_upload_dir = wp_upload_dir();
        $attachment = array(
            'guid' => $wp_upload_dir['url'].'/'.basename($movefile['file']),
            'post_mime_type' => $movefile['type'],
            'post_title' => preg_replace('/\.[^.]+$/', '', basename($movefile['file'])),
            'post_content' => '',
            'post_status' => 'inherit'
        );
      // on crée les informations et génère les thumnails
        $attach_id = wp_insert_attachment($attachment, $movefile['file']);
        $attach_data = wp_generate_attachment_metadata( $attach_id, $movefile['file'] );
        $update = wp_update_attachment_metadata( $attach_id,  $attach_data );
    }
}
?>