About PHP and gz-compression

Question

I was looking for gz-compression in PHP and I found this piece of code:

<?php function print_gzipped_output() { $HTTP_ACCEPT_ENCODING = $_SERVER["HTTP_ACCEPT_ENCODING"]; if( headers_sent() ) $encoding = false; else if( strpos($HTTP_ACCEPT_ENCODING, 'x-gzip') !== false ) $encoding = 'x-gzip'; else if( strpos($HTTP_ACCEPT_ENCODING,'gzip') !== false ) $encoding = 'gzip'; else $encoding = false; if( $encoding ) { $contents = ob_get_clean(); $_temp1 = strlen($contents); if ($_temp1 < 2048) // no need to waste resources in compressing very little data print($contents); else { header('Content-Encoding: '.$encoding); print("\x1f\x8b\x08\x00\x00\x00\x00\x00"); $contents = gzcompress($contents, 9); $contents = substr($contents, 0, $_temp1); print($contents); } } else ob_end_flush(); } ?>

My question is simple: what does the line

print("\x1f\x8b\x08\x00\x00\x00\x00\x00");

actually means?

Thank you in advance

Just a side note that compression is really much better handled by your web server. — Michael Mior
– Michael Mior, Commented Dec 25, 2011 at 5:32

Michael Mior · Accepted Answer · 2011-12-25 05:33:20Z

This is the header for gzip-format files. You can view more details here.

The first two bytes identify the file as gzipped. The following 8 specifies the use of the DEFLATE compression method. The final four zero bytes are for fields which aren't needed.

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