WordPressでHTTPからHTTPSへ移行する方法 (version5.7以降)

if ( 'update_https' === $action ) {
	check_admin_referer( 'wp_update_https' );

	if ( ! current_user_can( 'update_https' ) ) {
		wp_die( __( 'Sorry, you are not allowed to update this site to HTTPS.' ), 403 );
	}

	if ( ! wp_is_https_supported() ) {
		wp_die( __( 'It looks like HTTPS is not supported for your website at this point.' ) );
	}

	$result = wp_update_urls_to_https();

	wp_redirect( add_query_arg( 'https_updated', (int) $result, wp_get_referer() ) );
	exit;
}

/**
 * Update the 'home' and 'siteurl' option to use the HTTPS variant of their URL.
 *
 * If this update does not result in WordPress recognizing that the site is now using HTTPS (e.g. due to constants
 * overriding the URLs used), the changes will be reverted. In such a case the function will return false.
 *
 * @since 5.7.0
 *
 * @return bool True on success, false on failure.
 */
function wp_update_urls_to_https() {
	// Get current URL options.
	$orig_home    = get_option( 'home' );
	$orig_siteurl = get_option( 'siteurl' );

	// Get current URL options, replacing HTTP with HTTPS.
	$home    = str_replace( 'http://', 'https://', $orig_home );
	$siteurl = str_replace( 'http://', 'https://', $orig_siteurl );

	// Update the options.
	update_option( 'home', $home );
	update_option( 'siteurl', $siteurl );

	if ( ! wp_is_using_https() ) {
		// If this did not result in the site recognizing HTTPS as being used,
		// revert the change and return false.
		update_option( 'home', $orig_home );
		update_option( 'siteurl', $orig_siteurl );
		return false;
	}

	// Otherwise the URLs were successfully changed to use HTTPS.
	return true;
}

add_filter( 'the_content', 'wp_replace_insecure_home_url' );

/**
 * Replaces insecure HTTP URLs to the site in the given content, if configured to do so.
 *
 * This function replaces all occurrences of the HTTP version of the site's URL with its HTTPS counterpart, if
 * determined via {@see wp_should_replace_insecure_home_url()}.
 *
 * @since 5.7.0
 *
 * @param string $content Content to replace URLs in.
 * @return string Filtered content.
 */
function wp_replace_insecure_home_url( $content ) {
	if ( ! wp_should_replace_insecure_home_url() ) {
		return $content;
	}

	$https_url = home_url( '', 'https' );
	$http_url  = str_replace( 'https://', 'http://', $https_url );

	// Also replace potentially escaped URL.
	$escaped_https_url = str_replace( '/', '\/', $https_url );
	$escaped_http_url  = str_replace( '/', '\/', $http_url );

	return str_replace(
		array(
			$http_url,
			$escaped_http_url,
		),
		array(
			$https_url,
			$escaped_https_url,
		),
		$content
	);
}