The requested PHP extension intl is missing from your system (SonataAdminBundle) in Symfony2

Linux user

yum install php-intl

I had the same problem while I was installing new Magento 2.0, after different hit and trials, I manged to solve it by following these steps:

I copied all icu* files from php directory to Appache directory, and it worked.

Php direcotry:

WAMP\bin\php\php5.5.12

Appache Directory:

WAMP\bin\apache\apache2.4.9

Make sure to un-comment following line in php.ini file:

extension=ext/php_intl.dll

Like @Hugehornet pointed out - you should enable this extension in php.ini by uncommenting this line: extension=ext/php_intl.dll

If you use wamp's interface for this task you are actually updating the php.ini file located in apache's directory.

Example: C:\wamp\bin\apache\Apache2.4.4\bin\php.ini

Composer is using the one located in the php's installation directory.

Example: C:\wamp\bin\php\php5.4.12\php.ini

You should manually edit the latter and restart the wamp server.