Variables in php - you will know variables after studying in junior high school

When you were in junior high school. Teachers often teach you this.

Excuse me, Li Lei and Han Meimei, if:

x = 5
y = 6

Then what is x + y equal to? Everyone will answer without hesitation. x + y equals 11.

Next let’s look at the following junior high school mathematics knowledge. What is the result of x + y?

x = 5
y = 6
x ＝ 8

I guess everyone will answer without hesitation: the result of x + y is 14.

This is a variable!

Several characteristics of variables:

1.x = 5 Assign the value 5 on the right to x on the left

2. The second paragraph x = 8, and finally x + The result of y is equal to 14, indicating that x can be reassigned in the operation (execution) from top to bottom.

The same is true for our variables in PHP. But there are several characteristics:

1. It must start with $. For example, the variable , Chinese, _ is not a special symbol

5. Variable names must be meaningful (do not write variable names such as xxx, aaa, ccc)

Error examples:

Error: variable starts with a number

<?php
3 = 345;
?>

<?php
//$a*d = 345;

//$中国 = 123;
?>

<?php
$aaaaaaa = 345;
?>

Error: Variables are strictly case-sensitive. $dog and $Dog are variables of the PHP Academy. Try changing the value of $dog to 8. As a result, D is written in uppercase.

<?php
$dog = 5;
//重新修改$dog的值，将$dog改为8
$Dog = 8;
?>

Correct example:

Correct: A variable cannot start with a number, but a number can be sandwiched between and at the end of the variable name

<?php
$iphone6 = 5880;
$iphone6plus = 6088;
?>

<?php
$_cup = 123;
?>

$ is called the dollar sign, and the English word is: dollar. PHP variables must start with a dollar sign. It shows that there is a "money" way to engage in PHP.

dollar

Explanation: US dollar