Wordpress-import-image-from-url.php

<?php
    /*
        Function to import image from URL to WordPress media library and assign to a post
        @params
        $post_id - The post ID for which you need to assign the uploaded image as featured image
        $image_url - The external image URL which needs to be imported to WordPress media library
    */
    function import_featured_image_from_url( $post_id = '', $image_url ='' ) {
        //Check both post_id and image_url is not empty
        if($post_id == '' || $image_url == '') {
            return;
        }

        //Get the post title of the post_id
        $title = get_post_field( 'post_title', $post_id );
    
        //Handle Upload - Refer https://developer.wordpress.org/reference/functions/media_sideload_image/
        $attach_id = media_sideload_image($image_url, $post_id, null, 'id');

        //require_once(ABSPATH . 'wp-admin/includes/media.php'); //Include this if you are importing from root or outside of wp-content folder
        //require_once(ABSPATH . 'wp-admin/includes/file.php'); //Include this if you are importing from root or outside of wp-content folder
        
        // Make sure that this file is included, as wp_generate_attachment_metadata() depends on it.
        require_once( ABSPATH . 'wp-admin/includes/image.php' );

        // Generate the metadata for the attachment, and update the database record.
        $attach_data = wp_generate_attachment_metadata( $attach_id, get_attached_file( $attach_id ) );
        wp_update_attachment_metadata( $attach_id, $attach_data );

        //set ALT text
        update_post_meta($attach_id, '_wp_attachment_image_alt', $title);

        //Set default image title with post title
        $args=array(
            'ID' => $attach_id,
            'post_title' => $title
        );
        wp_update_post($args);

        //assign uploaded image as featured image for the post_id
        set_post_thumbnail( $post_id, $attach_id );
    }
?>