Variables of variables, PHP and you

In a project I worked on recently, I discovered a new concept about using variables in PHP. In my program, I need to update multiple records on one page at the same time. After a long period of painful thinking, the concept of variable variable accidentally flashed in my mind, and all the confusion disappeared. Swept away.
＜b>Introduction＜/b>
　What are variables called variables? According to the PHP manual, a variable is a variable that takes the value of a variable and uses it as the variable name of another variable. This statement seems quite straightforward and can easily be confused with those using the word "variable" in a sentence. To give a simple example, you define a variable --- x is equal to this --- and then define a variable of a variable, which means you use the value of x as the name of the new variable. In this example, the value of this new variable is is cake. It is expressed in PHP as follows:
＜?php
$x = "this";
$$x = "is cake";
?>
The symbol $$ is the representation of variables in PHP. Now we can refer to the two variables $x and $$x in two different ways.
＜?php
echo "$x ${$x}";
?>
＜?php
echo "$x $this";
?>
Both the above two programs will output this is cake. Note that $$x is written as ${$x} in the echo statement. This is to let PHP know that what you want to output is a variable variable rather than a $ character and $x variable.
　Are you still confused? Oh, maybe, you want some more in-depth and useful examples? In the next section, I will show you how to use variables to edit multiple records on one page.
＜b>Example＜/b>
　 Suppose you already have a MySQL database that saves links to some sites of interest. There is a table submissions in the database with the following fields:
SubmissionID
PostedBy
Link
Description
Approved
Now you want to display all the links in the table that have been created but not approved. The edit page should be able to correct some input errors and use the appropriate radio buttons to set the Approved for each record, and then Submit all updated records to the table at once.
　First, when you extract all the records from the database and display them, you must set a unique name for each record. This will allow us to identify the value of each record in a loop when submitting. The code is as follows:
＜?php
//Initialize the variable counter
$index = 0;
$index_count = 0;
echo "＜form method=post action=$PHP_SELF>n";
echo "＜table> n";
echo "