Shorten the string size

Question

Is there any way to shorten the size of the type string zipar she and then deszipar as the Base64 function does?

Answer 1

You have at least two alternatives to compress:

• gzcompress()

  This function compresses the string using the ZLIB data format.

  Decompress with gzuncompress().

• gzdeflate()

  This function compresses the string using the DEFLATE data format.

  Decompress with gzinflate().

A simple test reveals that gzdeflate achieves better results:

$tring = "Bubu votou para fechar!";

$compressed1 = gzcompress($tring, 9);

echo strlen($compressed1).PHP_EOL;    // 31 bytes

$compressed2 = gzdeflate($tring, 9);

echo strlen($compressed2).PHP_EOL;    // 25 bytes

See test on Ideone.

The improvement of results obtained in such a simple string is related to the fact that the function gzcompress() adds a 2 byte header and a 4 byte verification value at the end:

Which to use

In terms of compression, both present the same performance, but in terms of decompression, mainly with large data, the function gzinflate() is faster, performed almost half the time when compared to the gzuncompress().

In short:

If the data to compress is staying on the same machine, gzdeflate() seems to be the ideal option.

Portability

In terms of portability, the solution could pass through a third function.

To compress a string on a machine and decompress on a different machine, it is convenient to have some information about the work done:

• gzencode()

  This function returns a compressed version of input data compatible with gzip program output.

  That is, the output of the function contains the headers and the data structure, giving us a way to "move" the string safely compressed.

  Decompress with gzdecode().

A simple test reveals an increase in output size due to the control information present in it (headers and data structure):

$tring = "Bubu votou para fechar!";

$compressed3 = gzencode($tring, 9);

echo strlen($compressed3).PHP_EOL;    // 43 bytes

See test on Ideone.

Answer 2

Maybe this is what you’re looking for:

• Function gzcompress: used to compress a string, returning another string with the compressed content.

• Function gzuncompress: used to decompress a compressed string. Returning the original string.

Example:

$compressed = gzcompress('Compress me', 9);
$decompress = gzuncompress($compressed);
echo $compressed."\n";
echo $decompress;

Output:

x�s��-(J-.V�M��?
Compress me

Note: the compressed output was larger than the original, because the algorithm adds additional information to the compressed string, so it can decompress later. The larger the original string, the better the result.