deflate_init
Initialize an incremental deflate context
Description
DeflateContextfalse deflate_init(int $encoding, array $options = [])
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.