What are the allowed symbols for identifiers in PHP?

The symbols allowed for identifiers in php include letters, numbers, underscores and Chinese characters. Detailed introduction: 1. Letters and numbers. Identifiers can be composed of letters and numbers. They can start with a letter and can be followed by any number of letters, numbers or underscores; 2. Underline. Identifiers can contain underscores, but not underscores. beginning; 3. Chinese characters. Starting from PHP 7.2, Chinese characters are allowed to be used in identifiers. $Chinese variables, function Chinese functions (), etc. are all legal identifiers, etc.

The operating system of this tutorial: Windows10 system, PHP version 8.1.3, DELL G3 computer.

In PHP, identifiers are names used to identify named entities such as variables, functions, classes, and constants. Identifiers must follow certain naming rules, including the following aspects:

1. Letters and numbers: Identifiers can be composed of letters (case sensitive) and numbers. They can start with a letter and be followed by any number of letters, numbers, or underscores.

2. Underscore: Identifiers can contain underscores (_), but cannot start with underscores. For example, $my_variable, $user_name, etc. are all legal identifiers.

3. Reserved words: You cannot use reserved words in PHP as identifiers because these reserved words have special meanings and uses. For example, you cannot use if, else, for, class, etc. as identifiers.

4. Chinese characters: Starting from PHP 7.2, Chinese characters are allowed in identifiers. For example, $Chinese variable, function Chinese function (), etc. are all legal identifiers.

It should be noted that although PHP allows the use of some special characters in identifiers, in actual development, it is recommended to follow concise, clear and readable naming conventions to improve code readability and Maintainability. Here are some recommendations for naming conventions:

1. Use meaningful names: Identifiers should be descriptive and expressive, accurately reflecting the meaning and purpose of the entity they represent.

2. Follow camel case naming: In PHP, camel case naming is usually used to name variables, functions and classes. CamelCase nomenclature connects multiple words together, with the first letter of each word capitalized, such as $myVariable, getUserInfo().

3. Capitalize the first letter of class names: Class names should start with a capital letter to distinguish them from functions and variables. For example, class MyClass.

4. Constants are named in all uppercase letters: Constants are usually named in all uppercase letters, and underscores are used to separate words. For example, define("MAX_SIZE", 100).

To summarize, in PHP, the symbols allowed for identifiers include letters, numbers, and underscores. They can start with letters, but cannot start with numbers or underscores. Starting with PHP version 7.2, Chinese characters are also allowed in identifiers. In actual development, it is recommended to follow naming conventions, use meaningful names, and try to avoid using special characters and reserved words as identifiers. If you have any further questions please feel free to let me know.

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