1. If you are using CGI/FCGI
Refer to your phpinfo(), find the value for 'user_ini.filename'. It should be sth like .user.ini or php.ini
In your web root create a file with the filename you found above, (e.g. .user.ini). If it's already there open it with a text editor.
In it add the line
always_populate_raw_post_data = -1
2. If not
Open your .htaccess file with a text editor.
Add the following code
<IfModule mod_php5.c> php_flag always_populate_raw_post_data -1 </IfModule>