Reading And Writing To Compressed gzip Files

23rd April 2009 - 4 minutes read time
Reading and writing to compressed gzip files can be done in much the same way as reading and writing normal files. The main difference is the use of some special functions that compress and uncompress the data. Rather then use fopen() to open a file, you open a compressed file with gzopen(). This is the case for many of the file access functions, although you should be aware that they don't all work exactly the same as each other. Here are some examples of the compression functions in use. To read from a compressed file use the following script.
// read from file
$inputfile = 'text.gz';
 
$filecontents = '';
 
$ifh = gzopen($inputfile, 'r');
 
while ( $line = gzgets($ifh, 1024) ) {
    $filecontents .= $line;
}
echo $filecontents;
gzclose($ifh);
To write to a compressed file use the following script.
// writing to a complessed file
$inputfile = 'text.gz';
 
$string = 'lalalala';
$filecontents = '';
 
$ifh = gzopen($inputfile, 'r');
 
while ( $line = gzgets($ifh, 1024) ) {
    $filecontents .= $line;
}
gzclose($ifh);
 
$ifh = gzopen($inputfile, 'w');
if ( !gzwrite($ifh, $filecontents.$string) ) {
    // write failed
}
 
gzclose($ifh);
To compress a normal file use the following script.
// compress
$inputfile = 'text.txt';
$outputfile = 'text.gz';
 
// open files
$ifh = fopen($inputfile, 'rb');
$ofh =  fopen($outputfile, 'wb');
 
// encode string
$encoded = gzencode(fread($ifh, filesize($inputfile)));
 
if ( !fwrite($ofh, $encoded) ) {
    // write failed
}
 
// close files
fclose($ifh);
fclose($ofh);
To uncompress a gzip file use the following script.
// uncompress
$inputfile = 'text.gz';
$outputfile = 'text.txt';
 
$ofh =  fopen($outputfile, 'wb');
 
$string = '';
 
$ifh = gzopen($inputfile, 'r');
while ( $line = gzgets($ifh, 1024) ) {
    $string .= $line;
}
 
if ( !fwrite($ofh, $string) ) {
    // write failed
}
 
echo $string;
 
gzclose($ifh);
fclose($ofh);
Notice from these examples that you can open a compressed file using fopen(), but you need to use the 'b' flag to indicate to fopen that you want the file to be opened in a binary format. Basically, the two following calls are very much the same.
$ifh = gzopen($inputfile, 'r');
$ifh = fopen($inputfile, 'rb');
The gzopen() function can also take some other parameters as the mode. These include the compression level (eg. wb1 or wb9) or a strategy. The strategy can be either f for filtered (used as wb9f) or h for Huffman only compression (used as wb1h).
PHP

Add new comment

The content of this field is kept private and will not be shown publicly.
CAPTCHA
5 + 4 =
Solve this simple math problem and enter the result. E.g. for 1+3, enter 4.
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.

Related Content

Recreating Spotify Wrapped In PHP

17th March 2024

I quite like the end of the year report from Spotify that they call "Wrapped". This is a little application in which they tell you what your favorite artist was and what sort of genres you listened to the most during the year.

Read more

Should A Constructor Throw An Exception?

18th February 2024

Let's say you had a class that you wanted to use, but there was some sort of error in creating the object. This might be that the wrong parameters were passed, or the third party service (eg. a database) wasn't available at the time of creation.

Read more

PHP Question: Variable Reference

10th December 2023

Question

What does the following code print out?

function arrayPrint($array)
{
   echo implode(' ', $array);
}

$arrayA = [1, 2, 3];
$arrayB = $arrayA;
$arrayB[1] = 0;
arrayPrint($arrayA);

Read more

Creating An Authentication System With PHP and MariaDB

15th October 2023

Using frameworks to handle the authentication of your PHP application is perfectly fine to do, and normally encouraged. They abstract away all of the complexity of managing users and sessions that need to work in order to allow your application to function.

Read more

Creating Sparklines In PHP

17th September 2023

A sparkline is a very small line graph that is intended to convey some simple information, usually in terms of a numeric value over time. They tend to lack axes or other labels and are added to information readouts in order to expand on numbers in order to give them more context.

Read more