我在mac中使用php 5.5.27，当我运行$php app/console server:run时，我得到了：
[InvalidArgumentException]
There are no commands defined in the "server" namespace.
我还查看php -v的php版本，php app/check.php，它显示的是同一版本的PHP 5.5.27，有什么见解吗？
我用symfony-installer安装symfony，我的机器上已经安装了php。
即使我跑$php app/console，我也得到了：
Symfony version 2.0.12 - app/dev/debug
Usage:
[options] command [arguments]
Options:
--help -h Display this help message.
--quiet -q Do not output any message.
--verbose -v Increase verbosity of messages.
--version -V Display this application version.
--ansi Force ANSI output.
--no-ansi Disable ANSI output.
--no-interaction -n Do not ask any interactive question.
--shell -s Launch the shell.
--env -e The Environment name.
--no-debug Switches off debug mode.
Available commands:
help Displays help for a command
list Lists commands
assetic
assetic:dump Dumps all assets to the filesystem
assets
assets:install Installs bundles web assets under a public web directory
cache
cache:clear Clears the cache
cache:warmup Warms up an empty cache
container
container:debug Displays current services for an application
doctrine
doctrine:cache:clear-metadata Clears all metadata cache for a entity manager
doctrine:cache:clear-query Clears all query cache for a entity manager
doctrine:cache:clear-result Clears result cache for a entity manager
doctrine:database:create Creates the configured databases
doctrine:database:drop Drops the configured databases
doctrine:ensure-production-settings Verify that Doctrine is properly configured for a production environment.
doctrine:generate:crud Generates a CRUD based on a Doctrine entity
doctrine:generate:entities Generates entity classes and method stubs from your mapping information
doctrine:generate:entity Generates a new Doctrine entity inside a bundle
doctrine:generate:form Generates a form type class based on a Doctrine entity
doctrine:mapping:convert Convert mapping information between supported formats.
doctrine:mapping:import Imports mapping information from an existing database
doctrine:mapping:info Shows basic information about all mapped entities
doctrine:query:dql Executes arbitrary DQL directly from the command line.
doctrine:query:sql Executes arbitrary SQL directly from the command line.
doctrine:schema:create Executes (or dumps) the SQL needed to generate the database schema
doctrine:schema:drop Executes (or dumps) the SQL needed to drop the current database schema
doctrine:schema:update Executes (or dumps) the SQL needed to update the database schema to match the current mapping metadata
generate
generate:bundle Generates a bundle
generate:doctrine:crud Generates a CRUD based on a Doctrine entity
generate:doctrine:entities Generates entity classes and method stubs from your mapping information
generate:doctrine:entity Generates a new Doctrine entity inside a bundle
generate:doctrine:form Generates a form type class based on a Doctrine entity
init
init:acl Mounts ACL tables in the database
mopa
mopa:generate:crud Generates a CRUD based on a Doctrine entity
router
router:debug Displays current routes for an application
router:dump-apache Dumps all routes as Apache rewrite rules
swiftmailer
swiftmailer:spool:send Sends emails from the spool
它不会显示服务器命令：（