PHP variable naming rules

How to understand variables in php?

Variables in programs originate from mathematics and can be used in programming languages Store results or represent abstract concepts. Simply understand that a variable is a container for temporarily storing values. It can store numbers, text, and some complex data (such as strings, complex permutations, etc.). Variables are at the core of the PHP language and are the key to using PHP. , the value of the variable will change at any time during the running of the program. It can give a short and easy-to-remember name for a piece of data to be used in the program. In addition, it can also save the user input data and the results of special operations. In summary, variables are variables that are used for Simple tool to track almost any type of information.

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Variables in the php language

PHP data storage unit uses variables and constants to store various types of data. PHP is a weakly typed language. There is no need to declare variables before using them. Variables are created when assigning values. This reason makes PHP syntax is very different from C language and Java (strongly typed language).

Declaration and attention of PHP variables

Declaring variables in PHP must use a dollar sign "$" followed by the variable name, and then Use the assignment operator (=) to assign a value to a variable.

<?php
    $x=5;
    $y=6;
    $z=$x+$y;
    echo $z;
?>

PHP variables have a certain scope of use after they are declared. Most PHP variables are not declared in functions. Only a separate range from the declaration point to the end of the file is used. This separate range can be used in all of a page. Used in PHP mode, it also includes include and require files. During the variable usage period, you can use unset() to release the specified variable, use isset() to check whether the variable is set, and use isempty() to check whether the variable is empty.

php variable naming rules

　1. Case sensitive

　　$A and $a $ is two different variables (system built-in structures and keywords, user-defined class and function names are case-sensitive).

　2. The variable starts with the $ symbol, followed by the name of the variable.

　3. Variable names must start with letters or underscores and cannot start with numbers.

　4. Variable names can only contain alphanumeric characters and underscores (A-z, 0-9 and _)

If the variable is composed of letters, usually Use all lowercase letters as the last name. If the variable is made up of multiple characters, use all lowercase letters for the first letter and capitalize each subsequent letter. For example: $aaaBbbCcc style. It is recommended that you use this variable naming method. I will introduce PHP variables here today and continue to introduce them tomorrow. If you have any good ideas, you can discuss them together!

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