I installed apache2 and php with apt-get. But if i check which version did it install on packet manager it's 5.3.3-7
Can you tell me what 3-7 mean? Last version of php is 5.3.5.
5.3.3 = upstream_version 7 = debian_revision
The -7 on the end of the package is the version of that specific package, so there have been (at least) 7 different versions of the PHP 5.3.3 package. The security team takes bug fixes from newer versions of PHP and applies them to the old version so that everyone can keep the same version of PHP for years, ideally without running into incompatibilities when they upgrade. You can take a look at /usr/share/doc/php5-common/changelog.Debian.gz to see what changed in every version of the package.
It looks like even unstable (sid) doesn't have a package for 5.3.5 yet. If you absolutely need the latest and greatest, you'll need an alternate repository like this one.