Site Health Check for Compression and Browser Caching

add_filter( 'site_status_tests', function ( $tests ) {
    $tests['direct']['wpide_compression_cache'] = array(
        'label' => 'Compression and browser caching',
        'test'  => function () {
            $result = get_transient( 'wpide_compression_check' );

            if ( false === $result ) {
                $args = array( 'timeout' => 8, 'sslverify' => apply_filters( 'https_local_ssl_verify', false ), 'headers' => array( 'Accept-Encoding' => 'gzip, br' ), 'decompress' => false );
                $home = wp_remote_get( home_url( '/' ), $args );
                $css  = wp_remote_get( get_stylesheet_uri(), $args );
                $cc   = (string) wp_remote_retrieve_header( $css, 'cache-control' );
                $age  = preg_match( '/max-age=(\d+)/', $cc, $m ) ? (int) $m[1] : 0;
                $result = array(
                    'compressed' => ! is_wp_error( $home ) && '' !== (string) wp_remote_retrieve_header( $home, 'content-encoding' ),
                    'cached'     => ! is_wp_error( $css ) && ( $age >= 30 * DAY_IN_SECONDS || '' !== (string) wp_remote_retrieve_header( $css, 'expires' ) ),
                    'error'      => is_wp_error( $home ),
                );
                set_transient( 'wpide_compression_check', $result, 12 * HOUR_IN_SECONDS );
            }

            $problems = array();
            if ( ! $result['compressed'] ) {
                $problems[] = 'pages are not compressed with gzip or Brotli';
            }
            if ( ! $result['cached'] ) {
                $problems[] = 'static files such as CSS do not have a long browser cache lifetime';
            }

            return array(
                'label'       => $result['error'] ? 'Compression and caching could not be checked' : ( $problems ? 'Compression or browser caching is missing' : 'Compression and browser caching are enabled' ),
                'status'      => $problems ? 'recommended' : 'good',
                'badge'       => array( 'label' => 'Performance', 'color' => 'blue' ),
                'description' => '<p>' . esc_html( $problems ? 'Your server reports that ' . implode( ' and ', $problems ) . '. Ask your host to enable compression and long cache headers for static files.' : 'Text responses are compressed and static files are cached by browsers.' ) . '</p>',
                'test'        => 'wpide_compression_cache',
            );
        },
    );

    return $tests;
} );