Sometimes you want a variable to be accessible to all the templates you use. This is possible inside your app/config/config.yml file:
有时您希望有个变量能够被您所使用的所有模板访问，这可以在您app/config/config.yml文件中设定：

1. # app/config/config.yml 
2. twig: 
3.     # ... 
4.     globals: 
5.         ga_tracking: UA-xxxxx-x 

Now, the variable ga_tracking is available in all Twig templates:
现在，变量ga_tracking可以被所有Twig模板访问：

1. <p>Our google tracking code is: {{ ga_tracking }} </p> 

It's that easy! You can also take advantage of the built-in Service Parameters system, which lets you isolate or reuse the value:
这很容易！您也可以利用内建的服务参数系统，该系统可以让您隔离或重用该值：

1. ; app/config/parameters.yml 
2. [parameters] 
3.     ga_tracking: UA-xxxxx-x
   

1. # app/config/config.yml 
2. twig: 
3.     globals: 
4.         ga_tracking: %ga_tracking% 

The same variable is available exactly as before.
该变量同先前完全相同。