To install the intl extension on a Debian Lenny system, the following commands (as `root`) worked perfectly for me:
apt-get install php-pear php5-dev dh-make-php fakeroot libicu38 libicu-dev xsltproc
pear channel-update pear.php.net
pear upgrade PEAR
pecl channel-update pecl.php.net
pear install intl
Probably the first line can be replaced with just:
apt-get install php-pear php5-dev libicu38 libicu-dev
But, you may need some of the other packages.
1. test if it works with on command line “php -i | grep intl”
if it’s not correctly installed and doesn’t work it will show nothing.
2. I created the file /etc/php5/conf.d/intl.ini and only put the line extension=intl.so in that file (restart apache and done)
sudo apt-get install php5-intl