Upload an image as media and attach it to some post if need

Upload_an_image_as_media_and_attach_it_to_some_post_if_need.php

<?php
//// upload an image as media and attach it to some post if need ////
function upload_end_attach_image($image_url, $filename, $post_id = NULL) {
    $upload_dir = wp_upload_dir(); // Set upload folder
    $image_data = file_get_contents($image_url); // Get image data
    // Check folder permission and define file location

    // Check image file type
    $wp_filetype = wp_check_filetype($image_url, null);

    $filename .= ".{$wp_filetype['ext']}";

    if (wp_mkdir_p($upload_dir['path'])) {
        $file = $upload_dir['path'] . '/' . $filename;
    } else {
        $file = $upload_dir['basedir'] . '/' . $filename;
    }

    // Create the image  file on the server
    file_put_contents($file, $image_data);


    // Set attachment data
    $attachment = array(
        'post_mime_type' => $wp_filetype['type'],
        'post_title' => sanitize_file_name($filename),
        'post_content' => '',
        'post_status' => 'inherit'
    );

    // Create the attachment
    $attach_id = wp_insert_attachment($attachment, $file /* , $post_id */);

    // Include image.php
    require_once(ABSPATH . 'wp-admin/includes/image.php');

    // Define attachment metadata
    $attach_data = wp_generate_attachment_metadata($attach_id, $file);

    // Assign metadata to attachment
    wp_update_attachment_metadata($attach_id, $attach_data);

    // And finally assign featured image to post
    if($post_id)
        set_post_thumbnail($post_id, $attach_id);
    return $attach_id;
}