Upload a file to the WordPress Media Library programatically using the URL of the file
<?php
//$file = '/path/to/file.png';
$file = rtrim(ABSPATH, '/').parse_url( 'http://url-to-file/file.png' , PHP_URL_PATH);
$filename = basename($file);
$upload_file = wp_upload_bits($filename, null, file_get_contents($file));
if (!$upload_file['error']) {
$wp_filetype = wp_check_filetype($filename, null );
$attachment = array(
'post_mime_type' => $wp_filetype['type'],
'post_parent' => $parent_post_id,
'post_title' => preg_replace('/\.[^.]+$/', '', $filename),
'post_content' => '',
'post_status' => 'inherit'
);
$attachment_id = wp_insert_attachment( $attachment, $upload_file['file'], $parent_post_id );
if (!is_wp_error($attachment_id)) {
require_once(ABSPATH . "wp-admin" . '/includes/image.php');
$attachment_data = wp_generate_attachment_metadata( $attachment_id, $upload_file['file'] );
wp_update_attachment_metadata( $attachment_id, $attachment_data );
}
}