Getting Started with PHP Variables_PHP Tutorial

A variable is a container used to temporarily store values. These values ​​can be numbers, text, or much more complex data.

PHP has 8 types of variables.

It includes 4 scalar (single value) types - string (character), integer, floating point (decimal) and Boolean (TRUE or FALSE);

Two non-scalar (multi-valued) types - arrays and objects, as well as resources (which you will see when interacting with the database) and NULL (which is a special type that does not have any values).

================================================== =============================

PHP syntax rules:
1. The name of a variable—also called its identifier—must start with a dollar sign ($), for example, $name.
2. Variable names can contain a combination of letters, numbers and underscores, for example, $my_report1.
3. The first character after the dollar sign must be a letter or underscore (not a number).
4. Variable names in PHP are case-sensitive. This is a very important rule. This means that $name and $Name are distinct variables.

FAQ:

First, you can use the equal sign (=) (also called the assignment operator) to assign a value to a variable.

Second, variables can be printed without quotes; or variables can be printed within double quotes; but cannot print variables within single quotes .

<?php
	echo $name;				//无需引号即可打印变量
	echo "Hello, $name";	//在双引号内打印变量
	echo 'Hello, $name';	//在单引号内打印变量[会报错]
?>

================================================== =============================

【1】The most important consideration when creating variables is to use a consistent naming pattern. Some programmers prefer to use all lowercase letters for variable names, with underscores separating words ($first_name); some prefer to use an initial capital letter, such as: $FirstName (i.e. camel case).