CXLIII. 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: 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 prepend the filename or path with a 'zlib:' prefix when calling fopen().
In version 4.3.0, this special prefix has been changed to 'zlib://' to prevent ambiguities with filenames containing ':'.
This feature requires a C runtime library that provides the fopencookie() function. To my current knowledge the GNU libc is the only library that provides this feature.

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: Builtin 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.

表格 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 H。

以下是该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.

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

注: 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

本扩展模块未定义任何资源类型。

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)

例

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

例子 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
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 -- Alias of 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