# deflate_init

(PHP 7)

deflate_init — Initialize an incremental deflate context

### 说明

deflate_init ( int `$encoding` [, array `$options` = array() ] ) : resource

Initializes an incremental deflate context using the specified `encoding`.

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.)

### 参数

`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.

  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).

### 返回值

Returns a deflate context resource (zlib.deflate) on success, 或者在失败时返回 `FALSE`.

### 错误／异常

If an invalid option is passed to `options` or the context couldn't be created, an error of level `E_WARNING` is generated.

### 参见

- deflate_add() - Incrementally deflate data
- inflate_init() - Initialize an incremental inflate context