CLXXXVIII. Zlib Compression Functions

简介

This module enables you to transparently read and write gzip (.gz) compressed files, through versions of most of the filesystem functions which work with gzip-compressed files (and uncompressed files, too, but not with sockets).

注意: Version 4.0.4 introduced a fopen-wrapper for .gz-files, so that you can use a special zlib: URL to access compressed files transparently using the normal f*() file access functions if you prefix the filename or path with zlib: when calling fopen(). This feature requires a C runtime library that provides the fopencookie() function. Up to now the GNU libc seems to be the only library that provides this feature.
In PHP 4.3.0, zlib: has been changed to compress.zlib:// to prevent ambiguities with filenames containing ':' characters. The fopencookie() function is not longer required. More information is available in the section about the 节 called 压缩流 于附录 O.

需求

This module uses the functions of zlib by Jean-loup Gailly and Mark Adler. You have to use a zlib version >= 1.0.9 with this module.

安装

Zlib support in PHP is not enabled by default. You will need to configure PHP --with-zlib[=DIR]

PHP 的 Windows 版本已经内置该扩展模块的支持。无需加载任何附加扩展库即可使用这些函数。

注意: Built-in support for zlib on Windows is available with PHP 4.3.0.

运行时配置

这些函数的行为受 php.ini 的影响。

The zlib extension offers the option to transparently compress your pages on-the-fly, if the requesting browser supports this. Therefore there are three options in the configuration file php.ini.

表 1. Zlib Configuration Options

Name	Default	Changeable	Changelog
zlib.output_compression	"0"	PHP_INI_ALL	Available since PHP 4.0.5.
zlib.output_compression_level	"-1"	PHP_INI_ALL	Available since PHP 4.3.0.
zlib.output_handler	""	PHP_INI_ALL	Available since PHP 4.3.0.

有关 PHP_INI_* 常量进一步的细节与定义参见附录 I。

以下是配置选项的简要解释。

zlib.output_compression boolean/integer

Whether to transparently compress pages. If this option is set to "On" in php.ini or the Apache configuration, pages are compressed if the browser sends an "Accept-Encoding: gzip" or "deflate" header. "Content-Encoding: gzip" (respectively "deflate") and "Vary: Accept-Encoding" headers are added to the output. In runtime, it can be set only before sending any output.

This option also accepts integer values instead of boolean "On"/"Off", using this you can set the output buffer size (default is 4KB).

注意: output_handler must be empty if this is set 'On' ! Instead you must use zlib.output_handler.

zlib.output_compression_level integer

Compression level used for transparent output compression.

zlib.output_handler string

You cannot specify additional output handlers if zlib.output_compression is activated here. This setting does the same as output_handler but in a different order.

资源类型

This extension defines a file pointer resource returned by gzopen().

预定义常量

以下常量由本扩展模块定义，因此只有在本扩展模块被编译到 PHP 中，或者在运行时被动态加载后才有效。

FORCE_GZIP (integer)
FORCE_DEFLATE (integer)

范例

This example opens a temporary file and writes a test string to it, then it prints out the content of this file twice.

例 1. Small Zlib Example

<?php

$filename = tempnam('/tmp', 'zlibtest') . '.gz';
echo "<html>\n<head></head>\n<body>\n<pre>\n";
$s = "Only a test, test, test, test, test, test, test, test!\n";

// open file for writing with maximum compression
$zp = gzopen($filename, "w9");

// write string to file
gzwrite($zp, $s);

// close file
gzclose($zp);

// open file for reading
$zp = gzopen($filename, "r");

// read 3 char
echo gzread($zp, 3);

// output until end of the file and close it.
gzpassthru($zp);
gzclose($zp);

echo "\n";

// open file and print content (the 2nd time).
if (readgzfile($filename) != strlen($s)) {
        echo "Error with zlib functions!";
}
unlink($filename);
echo "</pre>\n</body>\n</html>\n";

?>

目录
gzclose -- Close an open gz-file pointer
gzcompress -- Compress a string
gzdecode -- Decodes a gzip compressed string
gzdeflate -- Deflate a string
gzencode -- Create a gzip compressed string
gzeof -- Test for end-of-file on a gz-file pointer
gzfile -- Read entire gz-file into an array
gzgetc -- Get character from gz-file pointer
gzgets -- Get line from file pointer
gzgetss -- Get line from gz-file pointer and strip HTML tags
gzinflate -- Inflate a deflated string
gzopen -- Open gz-file
gzpassthru -- Output all remaining data on a gz-file pointer
gzputs -- 别名 gzwrite()
gzread -- Binary-safe gz-file read
gzrewind -- Rewind the position of a gz-file pointer
gzseek -- Seek on a gz-file pointer
gztell -- Tell gz-file pointer read/write position
gzuncompress -- Uncompress a compressed string
gzwrite -- Binary-safe gz-file write
readgzfile -- Output a gz-file
zlib_get_coding_type -- Returns the coding type used for output compression