Changing Variable Values in PHP

A variable's value is not something rigidly attached to it. We can freely write some data into a variable, read it, then write something else - and so on. See the example:

php<?php
  $a = 1;  // writing the value 1 to the variable
  echo $a; // will output 1
  
  $a = 2;  // now writing the value 2, overwriting the value 1
  echo $a; // will output 2
?>

Задание 1

Create a variable $a. Write the value 10 into it, output it to the screen. Then write the value 20 into it, and output it to the screen.