无法将您的需求解析为一组可安装的软件包

我正在尝试安装一个Symfony项目，我从github的仓库克隆，但我有问题安装依赖项。

当我运行composer install时，结果如下:

Your requirements could not be resolved to an installable set of packages.
Problem 1
- Installation request for doctrine/mongodb 1.0.0-BETA1 -> satisfiable by doctrine/mongodb[1.0.0-BETA1].
- doctrine/mongodb 1.0.0-BETA1 requires ext-mongo * -> the requested PHP extension mongo is missing from your system.
Problem 2
- Installation request for symfony/icu 1.1.x-dev -> satisfiable by symfony/icu[1.1.x-dev].
- symfony/icu 1.1.x-dev requires lib-icu >=3.8 -> the requested linked library icu has the wrong version installed or is missing from your system, make sure to have the extension providing it.
Problem 3
- symfony/icu 1.1.x-dev requires lib-icu >=3.8 -> the requested linked library icu has the wrong version installed or is missing from your system, make sure to have the extension providing it.
- symfony/symfony 2.3.x-dev requires symfony/icu ~1.0 -> satisfiable by symfony/icu[1.1.x-dev].
- Installation request for symfony/symfony 2.3.x-dev -> satisfiable by symfony/symfony[2.3.x-dev].

这是composer.json

{
"name": "symfony/framework-standard-edition",
"description": "The '"Symfony Standard Edition'" distribution",
"autoload": {
    "psr-0": { "": "src/" }
},
"require": {
    "php": ">=5.3.3",
    "symfony/symfony": "2.3.*",
    "symfony/icu": "1.1.*",
    "doctrine/orm": "2.3.4",
    "doctrine/common": "2.3.0",
    "doctrine/mongodb-odm": "1.0.*@dev",
    "doctrine/mongodb-odm-bundle": "3.0.*@dev",
    "twig/twig": "v1.12.2",
    "twig/extensions": "v1.0.0",
    "monolog/monolog": "1.3.1",
    "symfony/monolog-bundle": "v2.3.0",
    "doctrine/doctrine-bundle": "v1.2.0",
    "doctrine/dbal": "v2.3.2",
    "doctrine/doctrine-fixtures-bundle": "2.2.*",
    "sensio/generator-bundle": "v2.3.4",
    "jdorn/sql-formatter": "v1.2.0",
    "gedmo/doctrine-extensions": "v2.3.5",
    "symfony/assetic-bundle": "2.4.*@dev",
    "symfony/swiftmailer-bundle": "master",
    "jms/security-extra-bundle": "1.1.*",
    "jms/di-extra-bundle": "1.0.*",
    "jms/debugging-bundle": "dev-master",
    "sensio/distribution-bundle": "2.3.*",
    "sensio/framework-extra-bundle": "2.3.*",
    "guzzle/guzzle": "*",
    "rezzza/mailchimp-bundle": "1.0.*@dev",
    "knplabs/gaufrette": "dev-master",
    "knplabs/knp-gaufrette-bundle": "0.2.*@dev",
    "imagine/Imagine": "dev-master",
    "stfalcon/tinymce-bundle": "v0.2.0",
    "gregwar/captcha-bundle": "dev-master",
    "friendsofsymfony/rest-bundle": "1.2.2",
    "jms/serializer-bundle": "0.13.0",
    "chromedia/utilities": "dev-master",
    "chromedia/security-token-bundle": "dev-master"
},
"scripts": {
    "post-install-cmd": [
        "Sensio''Bundle''DistributionBundle''Composer''ScriptHandler::buildBootstrap",
        "Sensio''Bundle''DistributionBundle''Composer''ScriptHandler::clearCache",
        "Sensio''Bundle''DistributionBundle''Composer''ScriptHandler::installAssets"
    ],
    "post-update-cmd": [
        "Sensio''Bundle''DistributionBundle''Composer''ScriptHandler::buildBootstrap",
        "Sensio''Bundle''DistributionBundle''Composer''ScriptHandler::clearCache",
        "Sensio''Bundle''DistributionBundle''Composer''ScriptHandler::installAssets"
    ]
},
"config": {
    "bin-dir": "bin"
},
"extra": {
    "symfony-app-dir": "app",
    "symfony-web-dir": "web"
},
"minimum-stability": "dev"
}

谢谢!