6: <link rel="canonical" href="<?php echo isset($canonical) ? $canonical : rtrim(SITE_URL . parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH), '/') . '/'; ?>">
15: <link rel="alternate" hreflang="en" href="<?php echo isset($canonical) ? $canonical : rtrim(SITE_URL . parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH), '/') . '/'; ?>">
16: <link rel="alternate" hreflang="x-default" href="<?php echo isset($canonical) ? $canonical : rtrim(SITE_URL . parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH), '/') . '/'; ?>">
18: <meta property="og:url" content="<?php echo isset($canonical) ? $canonical : rtrim(SITE_URL . parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH), '/') . '/'; ?>">

=== SITE_URL constant ===