What is case insensitive in php

The following are case-insensitive in PHP: 1. Function name; 2. Method name; 3. Class name; 4. NULL; 5. TRUE; 6. FALSE; 7. Keywords; 8. Magic constants are also not case-sensitive, but uppercase is recommended.

The operating environment of this tutorial: windows10 system, PHP7.1 version, DELL G3 computer

What is not case sensitive in php

1. Variable names are case-sensitive

2. Constant names are case-sensitive by default and are usually written in uppercase
 php.ini configuration item instructions are case-sensitive
For example, file_uploads = 1 cannot be written as File_uploads = 1
3. Function names, method names, and class names are not case-sensitive 
But it is recommended to use the same name as when defined
4. Magic constants are not case-sensitive, uppercase letters are recommended
Including: __LINE__, __FILE__ , __DIR__, __FUNCTION__, __CLASS__, __METHOD__, __NAMESPACE__. 
5, NULL, TRUE, FALSE are not case-sensitive
Summary: 
In PHP, function names (custom and built-in functions), method names, class names, and keywords are not case-sensitive; but variable names are case-sensitive. 
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