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 the
encoding 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_* 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 or ZLIB_ENCODING_GZIP.
- strategy
-
One of ZLIB_FILTERED,
ZLIB_HUFFMAN_ONLY, ZLIB_RLE,
ZLIB_FIXED or
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 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
is generated.
deflate_add
Zlib Functions