Index: src/wp-includes/wp-db.php
===================================================================
--- src/wp-includes/wp-db.php	(revision 27410)
+++ src/wp-includes/wp-db.php	(working copy)
@@ -1315,7 +1315,7 @@
 			$host = $this->dbhost;
 			$port_or_socket = strstr( $host, ':' );
 			if ( ! empty( $port_or_socket ) ) {
-				$host = strstr( $host, ':', true );
+				$host = substr( $host, 0, strpos( $host, ':' ) );
 				$port_or_socket = substr( $port_or_socket, 1 );
 				if ( 0 !== strpos( $port_or_socket, '/' ) ) {
 					$port = intval( $port_or_socket );