Shorthand Operations in PHP

Let's take the following code:

php<?php
  $num = 1;
  $num = $num + 2;
?>

As you can see, the variable is assigned its current value plus something else. For such operations, there is a special shorthand operator +=, see the example:

php<?php
  $num  = 1;
  $num += 3; // equivalent to $num = $num + 3;
?>

There are similar operators for other mathematical operations:

php<?php
  $num  = 2;
  $num -= 3; // equivalent to $num = $num - 3;
?>

php<?php
  $num  = 2;
  $num *= 3; // equivalent to $num = $num * 3;
?>

php<?php
  $num  = 2;
  $num /= 3; // equivalent to $num = $num / 3;
?>

php<?php
  $str  = 'a';
  $str .= 'b'; // equivalent to $str = $str . 'b';
?>

php<?php
  $num = 47;
  $num = $num + 7;
  $num = $num - 18;
  $num = $num * 10;
  $num = $num / 15;
  echo $num;
?>

php<?php
  $str = 'a';
  $str = $str . 'b';
  $str = $str . 'c';
  
  echo $str;
?>