title: upgrade Zend Framework 1.12 to 2.3
body: <p>i've got zend framework 1.12.5 on my CentOS6 server. but i'd like to upgrade to be Zend Framework 2.3. How can i upgrade it or i have to remove zf1 off first and reinstalling zf2 instead of upgrade?</p>
  
  <p>Thanks </p>