To install the PECL package uploadprogress on CentOS, we do:

1. Yum up some packages:
   # yum install php-pear php-devel httpd-devel
2. Install uploadprogress through PEAR:
   # pear install pecl/uploadprogress
3. Tell PHP to load uploadprogress:
   # echo extension=uploadprogress.so > /etc/php.d/uploadprogress.ini
4. Restart Apache:
   # /sbin/service httpd graceful