Variable references for PHP constants and variables

Variable Reference

Variable Reference Many teachers like to use C language pointers to explain. As people with so many years of development and teaching experience - most people who learn PHP don't understand C language at all.

Using a pointer in C language to explain variable reference, we feel that it is enough. Moreover, it is not conducive to learning by friends who do not have a foundation in C language.

Regarding the knowledge points of variable reference, please use our explanation as the basis for understanding!

Let’s compare the execution results of the two pieces of code:
There is no difference in the first piece of code. It is exactly the same as our original PHP code:

<?php

$fo = 5;
//$fo的值为5，将5赋值
$bar = $fo;
//$bar的值原来为5，现在将值改为6
$bar = 6;
//$bar的结果为6
echo $bar.'<br />';
//$fo的结果为5
echo $fo.'<br />';

?>

The second code:

<?php

$fo = 5;
//注意，加上了一个&符哟
$bar = &$fo;

$bar = 6;
//$bar的结果为6
echo $bar.'<br />';
//$fo的结果为6
echo $fo.'<br />';

?>

Why do both results become 6?

I often give you this example. We can imagine it this way: a variable name corresponds to a data value. As shown below:

And adding & (after the and character) points the variables to the same storage space, as shown below:

That is, no matter how the value of $fo or $bar changes, $fo changes to $bar, and $bar changes, $fo will also change.

Let me give you an unreliable example to help you understand:
You have a puppy at home called Wangcai. There is another puppy named Goudan. One day, you ate the dog’s eggs. If you give the name Goudan to Wangcai

, then whether you hit Goudan or Wangcai, you will hit the same dog.

Note: If you understand, know, and are familiar with C language pointers. You can use pointers to understand it yourself, which is beyond the scope of this article.