下面php代码通过gzcompress和gzuncompress压缩和解压缩字符串，可以设定压缩级别

$str = 'Hello I am a very very very very long string';
$compressed = gzcompress($str, 9);//压缩级别为9
$uncompressed = gzuncompress($compressed);
 
echo $str, "\n";
echo $uncompressed, "\n";
echo base64_encode($compressed), "\n";
echo bin2hex($compressed), "\n";
echo urlencode($compressed), "\n";