PHP dagi qisqartirilgan amallar

Mana shunday kod berilgan bo'lsin:

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

Ko'rib turganingizdek, bu yerda o'zgaruvchiga uning joriy qiymati va yana biror narsa qo'shiladi. Bunday amallar uchun maxsus qisqartirilgan += operatori mavjud, misolni ko'ring:

php<?php
  $num  = 1;
  $num += 3; // $num = $num + 3; ga teng
?>

Qolgan matematik amallar uchun ham shunday operatorlar mavjud:

php<?php
  $num  = 2;
  $num -= 3; // $num = $num - 3; ga teng
?>

php<?php
  $num  = 2;
  $num *= 3; // $num = $num * 3; ga teng
?>

php<?php
  $num  = 2;
  $num /= 3; // $num = $num / 3; ga teng
?>

php<?php
  $str  = 'a';
  $str .= 'b'; // $str = $str . 'b'; ga teng
?>

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;
?>