// Update php.ini: (global is usually found at /etc/php.ini)
zlib.output_compression = On

OR

// Update .htaccess file with:
php_flag zlib.output_compression On
 
OR
  
// Add a line at the top your PHP code:
ini_set('zlib_output_compression','On');

http://zoocha.com

Active gzip on a linux server running PHP

php

PHP