php curl lib is just a wrapper of cUrl, so, first of all, you should install cUrl. Download the cUrl source to your linux server. Then, use the follow commands to install:
tar zxvf cUrl_src_taz
cd cUrl_src_taz
./configure --prefix=/curl/install/home
make
make test (optional)
make install
ln -s /curl/install/home/bin/curl-config /usr/bin/curl-config
Then, copy the head files in the "/curl/install/home/include/" to "/usr/local/include". After all above steps done, the php curl extension configuration could find the original curl, and you can use the standard php extension method to install php curl.
Hope it helps you, :)