Tive o mesmo problema, tive que desinstalar já instalado o libuv0.10 e o libuv0.10-dev.
Em seguida, siga estas instruções:
sudo apt-get install php-pear php5-dev libgmp-dev libpcre3-dev g++ make cmake libssl-dev openssl<br />
wget downloads.datastax.com/cpp-driver/ubuntu/14.04/dependencies/libuv/v1.8.0/libuv_1.8.0-1_amd64.deb<br />wget downloads.datastax.com/cpp-driver/ubuntu/14.04/dependencies/libuv/v1.8.0/libuv-dev_1.8.0-1_amd64.deb<br />
wget downloads.datastax.com/cpp-driver/ubuntu/14.04/cassandra/v2.4.2/cassandra-cpp-driver_2.4.2-1_amd64.deb<br />
wget downloads.datastax.com/cpp-driver/ubuntu/14.04/cassandra/v2.4.2/cassandra-cpp-driver-dev_2.4.2-1_amd64.deb
sudo dpkg -i libuv_1.8.0-1_amd64.deb<br />
sudo dpkg -i libuv-dev_1.8.0-1_amd64.deb<br />
sudo dpkg -i cassandra-cpp-driver_2.4.2-1_amd64.deb<br />
sudo dpkg -i cassandra-cpp-driver-dev_2.4.2-1_amd64.deb<br />
pecl install cassandra
ADD extension=cassandra.so in php.ini
Fonte: link