yii1.4constant.php, Yii2 alias is simple to use

First of all, what is an alias. There are many paths in Yii ， We will also use some paths during the development process. Generally speaking, you need to use absolute paths，but absolute paths are very long. So ， for the convenience of using paths， you can give each path a name in Yi ， this name is an alias.

Look directly at the example ：

The first usage ：

First set an alias ：Yii::setAlias( & # 39; & # 64; ww & # 39;, & # 39; 123 & # 39;);

Now you can get ： echo Yii::getAlias(& # 39; & #64;ww');//The result is 123

If you did not write the ‘@’ symbol ：echo Yii::getAlias('ww& #39;);//The result is the direct output of the ww string

The second usage ：

As mentioned earlier, the alias of ， is for the convenience of using the path ，Then look at specific examples：

For example ，Your project often uses some frequently used constants，You can create a new constant under config .php，

constant.php Code:

When you ， want to use this constant in the controller， you must import this file

You can write like this: include_once(realpath(dirname(__FILE__).'../../config')).'/constant.php';

Or use an alias to introduce: include_once(Yii::getAlias(“@app/config/constant.php”));

The third usage ：

This usage is in the second optimization, we can write a sentence in the configuration file (web.php) (note that ：aliases and components are at the same level，do not Write the following code into components)’aliases’=>['@ww'=>dirname(__FILE__).'/constant .php',],

Also write include_once(Yii::getAlias('@ww')); in the controller as well