+/**
+ * Set the scheme for a URL
+ *
+ * @since 3.4.0
+ *
+ * @param string $url Absolute url that includes a scheme
+ * @param string $scheme Optional. Scheme to give $url. Currently 'http', 'https', 'login', 'login_post', 'admin', or 'relative'.
+ * @return string $url URL with chosen scheme.
+ */
+function set_url_scheme( $url, $scheme = null ) {
+ $orig_scheme = $scheme;
+
+ if ( ! $scheme ) {
+ $scheme = is_ssl() ? 'https' : 'http';
+ } elseif ( $scheme === 'admin' || $scheme === 'login' || $scheme === 'login_post' || $scheme === 'rpc' ) {
+ $scheme = is_ssl() || force_ssl_admin() ? 'https' : 'http';
+ } elseif ( $scheme !== 'http' && $scheme !== 'https' && $scheme !== 'relative' ) {
+ $scheme = is_ssl() ? 'https' : 'http';
+ }
+
+ $url = trim( $url );
+ if ( substr( $url, 0, 2 ) === '//' )
+ $url = 'http:' . $url;
+
+ if ( 'relative' == $scheme ) {
+ $url = ltrim( preg_replace( '#^\w+://[^/]*#', '', $url ) );
+ if ( $url !== '' && $url[0] === '/' )
+ $url = '/' . ltrim($url , "/ \t\n\r\0\x0B" );
+ } else {
+ $url = preg_replace( '#^\w+://#', $scheme . '://', $url );
+ }
+
+ /**
+ * Filter the resulting URL after setting the scheme.
+ *
+ * @since 3.4.0
+ *
+ * @param string $url The complete URL including scheme and path.
+ * @param string $scheme Scheme applied to the URL. One of 'http', 'https', or 'relative'.
+ * @param string $orig_scheme Scheme requested for the URL. One of 'http', 'https', 'login',
+ * 'login_post', 'admin', 'rpc', or 'relative'.
+ */
+ return apply_filters( 'set_url_scheme', $url, $scheme, $orig_scheme );
+}
+