id()
id() : string
The stable identifier recorded in a frame header.
Returns
string —A short lowercase token such as "zstd", "gzip" or "none".
Stores frames verbatim.
Not a placeholder. Two real cases need it: already-compressed payloads such as media blocks, where compression spends CPU to add bytes, and a calibration baseline, where the ratio of every other codec is measured against this one.
levels() : array{min: int, max: int, default: int, fast: int, dense: int}
The compression levels this codec accepts.
The usable range, the default, the level to use on the flush path where throughput matters, and the level to use during compaction where ratio matters.
compress(string $data, ?int $level = null, ?string $dictionary = null) : string
Compresses a buffer.
| string | $data | The bytes to compress. An empty string compresses to an empty string, so that an absent payload never becomes a non-empty frame. |
| ?int | $level | A level within CompressionCodecInterface::levels(), or NULL for the default. |
| ?string | $dictionary | Raw dictionary bytes, or NULL. Ignored by codecs that report no dictionary support, so a caller never has to branch on it. |
The compressed bytes.