bzcompress

(PHP 4 >= 4.0.4, PHP 5)

bzcompress — Compress a string into bzip2 encoded data

说明

mixed bzcompress ( string $source [, int $blocksize = 4 [, int $workfactor = 0 ]] )

bzcompress() compresses the given string and returns it as bzip2 encoded data.

参数

source

The string to compress.

blocksize

Specifies the blocksize used during compression and should be a number from 1 to 9 with 9 giving the best compression, but using more resources to do so.

workfactor

Controls how the compression phase behaves when presented with worst case, highly repetitive, input data. The value can be between 0 and 250 with 0 being a special case.

Regardless of the workfactor, the generated output is the same.

返回值

The compressed string, or an error number if an error occurred.

范例

Example #1 Compressing data


<?php
$str = "sample data";
$bzstr = bzcompress($str, 9);
echo $bzstr;
?>

参见

bzdecompress() - Decompresses bzip2 encoded data

PHP手册 - N: Compress a string into bzip2 encoded data

用户评论:

uprz23 at gmail dot com (24-Jun-2010 08:52)

Comparing gzcompress/gzuncompress and bzcompress/bzdecompress, the bz combo is about 5x slower than gz.

diego a messenger do dsemmler do de (24-Apr-2009 11:01)

The blocksize parameter tells bzip to use 100 000 Byte * blocksize blocks to compress the string. In the example above we can see the output size and time needed of bz[2] to bz[9] are nearly the same, because there ware just 189 058 Byte of data to compress and in this case bz[2] to bz[9] means "compress all data et once". So we may notice a bigger difference in speed and compression rate with bigger files. the workfactor parameter sets, how fast bzip switches in the slower fallback algorithm, if the standard algorithm gets problems with much repetitive data. 0 means, bzip uses the default value of 30. This option is recommend. For more information about the parameter look at http://www.bzip.org/1.0.3/html/low-level.html#bzcompress-init

plasma (07-Sep-2008 06:39)

Here is a benchmark comparing strengths of bzip and gzip compression: gz[0] - 1.647ms - 189058 Byte (100%) gz[1] - 3.333ms - 44572 Byte (23.58%) gz[2] - 3.519ms - 42685 Byte (22.58%) gz[3] - 4.713ms - 40840 Byte (21.6%) gz[4] - 5.274ms - 39111 Byte (20.69%) gz[5] - 6.526ms - 37039 Byte (19.59%) gz[6] - 8.036ms - 36206 Byte (19.15%) gz[7] - 9.098ms - 35940 Byte (19.01%) gz[8] - 12.87ms - 35713 Byte (18.89%) gz[9] - 14.319ms - 35707 Byte (18.89%) bz[1] - 40.282ms - 32247 Byte (17.06%) bz[2] - 43.716ms - 29690 Byte (15.7%) bz[3] - 43.765ms - 29690 Byte (15.7%) bz[4] - 44.213ms - 29690 Byte (15.7%) bz[5] - 43.704ms - 29690 Byte (15.7%) bz[6] - 43.814ms - 29690 Byte (15.7%) bz[7] - 43.934ms - 29690 Byte (15.7%) bz[8] - 43.725ms - 29690 Byte (15.7%) bz[9] - 45.129ms - 29690 Byte (15.7%)