Connect via unix socket instead of filesystem to be compatible with p…

…hp open_basedir restrictions.

copied from #425

object-cache.php

@@ -1256,7 +1256,7 @@ public function build_client_parameters( $redis_server ) {
 			}
 		}
 
-		if ( file_exists( $redis_server['host'] ) && 'socket' === filetype( $redis_server['host'] ) ) { // unix socket connection.
+		if ( strpos($redis_server['host'], 'unix:///') === 0 ) ) { // Unix socket connection.
 			// port must be null or socket won't connect.
 			$port = null;
 		} else { // tcp connection.
@@ -1470,9 +1470,9 @@ protected function _exception_handler( $exception ) {
 		try {
 			$this->last_triggered_error = 'WP Redis: ' . $exception->getMessage();
 			// Be friendly to developers debugging production servers by triggering an error.
-			
+
 			// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_trigger_error,WordPress.Security.EscapeOutput.OutputNotEscaped
-			trigger_error( $this->last_triggered_error, E_USER_WARNING ); 
+			trigger_error( $this->last_triggered_error, E_USER_WARNING );
 		} catch ( PHPUnit_Framework_Error_Warning $e ) { // phpcs:ignore Generic.CodeAnalysis.EmptyStatement.DetectedCatch
 			// PHPUnit throws an Exception when `trigger_error()` is called. To ensure our tests (which expect Exceptions to be caught) continue to run, we catch the PHPUnit exception and inspect the RedisException message.
 		}