What are the magic variables in PHP?

Magic variables in PHP include "__LINE__", "__FILE__", "__DIR__", "__FUNCTION__", "__CLASS__", "__TRAIT__", "__METHOD__", "__NAMESPACE__" and "__NAMESPACE__", etc. Detailed introduction: 1. __LINE__ variable, a digital representation of the current code line number, which is very useful for debugging and error tracking; 2. __FILE__ variable, etc.

The operating environment of this tutorial: Windows 10 system, PHP8.1.3 version, Dell G3 computer.

Magic Variables in PHP are special predefined variables that are named in a specific format and are used to provide information about the script execution environment. In PHP, there are many magic variables that can be used. The following is an introduction to some common magic variables.

1. __LINE__: The numerical representation of the current code line number. This is useful for debugging and error tracing.

2. __FILE__: The full path and file name of the current script. This is especially useful when you need to reference files.

3. __DIR__: The directory where the current script is located. In contrast to __FILE__, it does not include the file name.

4. __FUNCTION__: The name of the current function or method.

5. __CLASS__: The name of the current class.

6. __TRAIT__: The name of the current trait. Traits are a way of combining code to reuse a collection of methods within a class.

7. __METHOD__: The name of the current method. If the method is in a class, the class name and method name are returned.

8. __NAMESPACE__: The name of the current namespace.

9. __NAMESPACE__ is empty for the global space. When code is executed in a namespace, it returns the current namespace name.

These magic variables can be used in code by directly referencing their names. For example, if we want to print the current line number in the code, we can use the __LINE__ variable as follows:

```
php
echo "当前行号：" . __LINE__;
```
同样，如果我们想要获取当前脚本的文件名和完整路径，可以使用__FILE__变量，如下所示：
```php
echo "当前脚本路径：" . __FILE__;
```

These magic variables are very useful when debugging code and logging. By using them, we can easily obtain important information about the code and execution environment to better understand and solve problems.

To summarize, magic variables in PHP are special predefined variables that provide information about the script execution environment. By using these variables, we can easily obtain code line number, file name, function name, class name and other information for debugging and error tracking.

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