调用未定义的函数Cassandra \\ Cluster \\ cassandra_cluster_new（）

I'm getting this error when I tried to insert data to cassandra using library datastax php driver. I'm using REST. Any idea ?

curl --data "x=y&a=b" my_api_url



PHP Fatal error: 
Call to undefined function Cassandra\\Cluster\\cassandra_cluster_new() 
in /prejectdir/datastax/php-driver/src/Cassandra/Cluster/Builder.php on line 142