laravel连接mongodb的问题 composer require jenssegers/mongodb 执行这个命令就报错

运行命令之后出现
Using version ^3.0 for jenssegers/mongodb
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

Problem 1
- jenssegers/mongodb v3.0.0 requires mongodb/mongodb ^1.0.0 -> satisfiable by mongodb/mongodb[1.0.0, 1.0.1, 1.0.2].
- jenssegers/mongodb v3.0.1 requires mongodb/mongodb ^1.0.0 -> satisfiable by mongodb/mongodb[1.0.0, 1.0.1, 1.0.2].
- jenssegers/mongodb v3.0.2 requires mongodb/mongodb ^1.0.0 -> satisfiable by mongodb/mongodb[1.0.0, 1.0.1, 1.0.2].
- mongodb/mongodb 1.0.2 requires ext-mongodb ^1.1.0 -> the requested PHP extension mongodb is missing from your system.
- mongodb/mongodb 1.0.1 requires ext-mongodb ^1.1.0 -> the requested PHP extension mongodb is missing from your system.
- mongodb/mongodb 1.0.0 requires ext-mongodb ^1.1.0 -> the requested PHP extension mongodb is missing from your system.