what are variables in php

Variables are containers used to store data. Variables in PHP start with the $ symbol, followed by the variable name.

Naming rules for variable names

In addition to requiring "$" to identify variable names, there are some rules that need to be followed. Just like after getting a driver's license, you still have to obey the traffic rules. There are three main naming rules for variable names:

1. The variable name must start with a letter or underscore "_", such as "$_name", "$name", "$name2", etc., but "$9name" "It's not right.

2. Variable names can only consist of letters, numbers, and "_", and can also contain Chinese characters. Such as "$_qq", "$qq308", "$my_apple", "such as "$name I'll wait", but

is "$name*" which is incorrect.

3. Variable names are not allowed to contain spaces. When the variable name consists of multiple words, it is recommended to use "_" to separate them (such as $my_apple), commonly known as the underscore method, or start with capital letters

such as $myApple, commonly known as camel formula naming method (also called camel case naming method).

It is particularly important to note that variable names in PHP are case-sensitive, such as "$my_book" and "$my_Book" represent two different variables .

<?php
    $my_book = "我的小写的book";
    $my_BOOK = "我的大写的BOOK";
 echo $my_book;
 echo "<br />";
 echo $my_BOOK;
 echo "<br />";
 $my_book = "这次奇迹要发生啦";
 echo $my_book;
 echo "<br />";
?>

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