PHP: Hypertext Preprocessor (original) (raw)

deflate_init

(PHP 7, PHP 8)

deflate_init — Initialize an incremental deflate context

Description

Note that the window option here only sets the window size of the algorithm, differently from the zlib filters where the same parameter also sets the encoding to use; the encoding must be set with theencoding parameter.

Limitation: there is currently no way to set the header information on a GZIP compressed stream, which are set as follows: GZIP signature (\x1f\x8B); compression method (\x08 == DEFLATE); 6 zero bytes; the operating system set to the current system (\x00 = Windows, \x03 = Unix, etc.)

Parameters

encoding

One of the [ZLIB_ENCODING_*](zlib.constants.php#constant.zlib-encoding-raw) constants.

options

An associative array which may contain the following elements:

level

The compression level in range -1..9; defaults to -1.

memory

The compression memory level in range 1..9; defaults to 8.

window

The zlib window size (logarithmic) in range 8..15; defaults to 15. zlib changes a window size of 8 to 9, and as of zlib 1.2.8 fails with a warning, if a window size of 8 is requested for [ZLIB_ENCODING_RAW](zlib.constants.php#constant.zlib-encoding-raw) or [ZLIB_ENCODING_GZIP](zlib.constants.php#constant.zlib-encoding-gzip).

strategy

One of [ZLIB_FILTERED](zlib.constants.php#constant.zlib-filtered),[ZLIB_HUFFMAN_ONLY](zlib.constants.php#constant.zlib-huffman-only), [ZLIB_RLE](zlib.constants.php#constant.zlib-rle),[ZLIB_FIXED](zlib.constants.php#constant.zlib-fixed) or**[ZLIB_DEFAULT_STRATEGY](zlib.constants.php#constant.zlib-default-strategy)** (the default).

dictionary

A string or an array of strings of the preset dictionary (default: no preset dictionary).

Return Values

Returns a deflate context resource (zlib.deflate) on success, or [false](reserved.constants.php#constant.false) on failure.

Errors/Exceptions

If an invalid option is passed to options or the context couldn't be created, an error of level [E_WARNING](errorfunc.constants.php#constant.e-warning) is generated.

Changelog

Version	Description
8.0.0	On success, this function returns a DeflateContext instance now; previously, a resource was returned.