Zlib Compression Functions

&reftitle.intro; 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). 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.

&reftitle.required; 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.

&reftitle.runtime; The zlib extension offers the option to transparently compress your pages on-the-fly, if the requesting browser supports this. Therefore there are two options in the configuration file &php.ini;. Zlib Configuration Options Name Default Changeable zlib.output_compression "0" PHP_INI_ALL zlib.output_compression_level "-1" PHP_INI_ALL

For further details and definition of the PHP_INI_* constants see ini_set. Here is a short explanation of the configuration directives. 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. You can use ini_set to disable this in your script if the headers aren't already sent. If you output a "Content-Type: image/" header the compression is disabled, too (in order to circumvent a Netscape bug). You can reenable it, if you add "ini_set('zlib.output_compression', 'On')" after the header call which added the image content-type. This option also accepts integer values instead of boolean "On"/"Off", using this you can set the output buffer size. zlib.output_compression_level integer Compression level used for transparent output compression.

&reftitle.resources; &no.resource;

&reference.zlib.constants;

&reftitle.examples; This example opens a temporary file and writes a test string to it, then it prints out the content of this file twice. Small Zlib Example \n\n\n

\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
print gzread($zp, 3);

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

print "\n";

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

\n\n\n"; ?> ]]>