Tipos de recursos
xdiff Functions
xdiff
PHP Manual

# Constantes predefinidas

Estas constantes están definidas por esta extensión y estarán disponibles solamente cuando la extensión ha sido o bien compilada dentro de PHP o grabada dinámicamente en tiempo de ejecución.

`XDIFF_PATCH_NORMAL` (integer)
  This flag indicates that xdiff_string_patch() and xdiff_file_patch() functions should create result by applying patch to original content thus creating newer version of file. This is the default mode of operation.
`XDIFF_PATCH_REVERSE` (integer)
  This flag indicated that xdiff_string_patch() and xdiff_file_patch() functions should create result by reversing patch changed from newer content thus creating original version.

Tipos de recursos
xdiff Functions
xdiff
PHP Manual