将php5.6降级为php5.5

Question

I am trying to downgrade my php version from 5.6 to 5.6 here is what I have tried so far :

add-apt-repository ppa:ondrej/php5-oldstable
apt-get update
apt-cache policy php5

the output the last command was :

installé : 5.6.11+dfsg-lubuntu3.1
candidat : 5.6.11+dfsg-lubuntu3.1

I expected the output to be something like 5.5 as I added old php repository. things like :

apt-get install php5=5.5.24

did not work either.

Thanks for your help