E: Unable to locate package

I am new to php and drupal.my problem is i tried to install php and related pkgs in terminal.I followed this command to install php5

sudo apt-get install php5 php5-cli php5-common php5-devel php5-mbstring php5-gd php5-mysql php5-pdo php5-xmlrpc php5-xml php5-pear

after i entered this command i saw the error like as below.
E: Unable to locate package php5-devel
E: Unable to locate package php5-mbstring
E: Unable to locate package php5-pdo
E: Unable to locate package php5-xml
E: Unable to locate package php5-pear
I tried many ways to get solution for this but i didn't got solution to this.After many hours i taken reinstall ubuntu after that again same error is shows me. Can any one help me from this headache error.