oggvorbis
PHP Manual

Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

OGG/Vorbis supports PCM encodings in the following formats
Constant Definition
OGGVORBIS_PCM_U8 Unsigned 8-bit PCM.
OGGVORBIS_PCM_S8 Signed 8-bit PCM.
OGGVORBIS_PCM_U16_LE Unsigned 16-bit PCM. Little Endian byte order.
OGGVORBIS_PCM_U16_BE Unsigned 16-bit PCM. Big Endian byte order.
OGGVORBIS_PCM_S16_LE Signed 16-bit PCM. Little Endian byte order.
OGGVORBIS_PCM_S16_BE Signed 16-bit PCM. Big Endian byte order.

oggvorbis
PHP Manual