WordPress

wp_upload_from_url.php

<?php
// Upload image from url 
// Returns an array (attachment_id, url), or false
function media_import_from_url( $url ) {
	$filename = basename($url);

	global $wpdb;
	$query = "SELECT post_id FROM {$wpdb->postmeta} WHERE meta_value LIKE '%/$filename'";
	$count = intval($wpdb->get_var($query));

	if ( $count != 0 ) {
		return array(
			'attachment_id' => $count,
			'url' => wp_get_attachment_image_url( $count, 'full' )
		);
	}

	$upload_file = wp_upload_bits($filename, null, file_get_contents($url)); // use url_get_contents cURL if file_get_contents() false
	if (!$upload_file['error']) {
		$wp_filetype = wp_check_filetype($filename, null );
		$attachment = array(
			'post_mime_type' => $wp_filetype['type'],
			'post_title' => preg_replace('/\.[^.]+$/', '', $filename),
			'post_content' => '',
			'post_status' => 'inherit'
		);
		$attachment_id = wp_insert_attachment( $attachment, $upload_file['file'] );
		if (!is_wp_error($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 );

			return array(
				'attachment_id' => $attachment_id,
				'url' => $upload_file['url']
			);
		}
	}

	return false;
}

function url_get_contents ($Url) {
    if (!function_exists('curl_init')){ 
        die('CURL is not installed!');
    }
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $Url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    $output = curl_exec($ch);
    curl_close($ch);
    return $output;
}