$string = 'Kompress aku...';
$compressed = gzdeflate($string, 9);
$fh = fopen('file.gz', 'w');
fwrite($fh, $compressed);
fclose($fh);

$fh = fopen('file.gz', 'r');
$read = fread($fh, filesize('file.gz'));
$uncompressed = gzinflate($read);
fclose($fh);
echo $uncompressed; // Kompress aku...