First of all you need to install an additional module first.
Unfortunately it seems that there is no such a module for writting to zip but there is a module for gzip, called "Zlib Compression Functions".
I dopn't know if this helps.
(FROM PHP Manual)
This example opens a temporary file and writes a test string to it, then it prints out the content of this file twice.
Example 1. Small Zlib Example
<?php
$filename = tempnam ('/tmp', 'zlibtest').'.gz';
print "<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
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 "</pre>\n</h1></body>\n</html>\n";
?>