Kipengele cha Kuunganisha na null katika PHP

Wacha tuchunguze msimbo ufuatao:

php<?php
  if (isset($arr['test'])) {
    $elem = $arr['test'];
  } else {
    $elem = 'empty';
  }
?>

Msimbo huu unaweza kuandikwa tena kwa kutumia kipengele cha ternary:

php<?php
  $elem = isset($arr['test']) ? $arr['test'] : 'empty';
?>

Hata hivyo, toleo la kwanza la msimbo, na la pili, zinasababisha usumbufu fulani. Ili kurahisisha miundo kama hii, kipengele cha kuunganisha na null kilibuniwa, kinachowakilisha amri ??. Wacha tuandike tena msimbo wetu kupitia kipengele hiki:

php<?php
  $elem = $arr['test'] ?? 'empty';
?>

php<?php
  $user = ['name' => 'john', 'age' => 30];
  
  if (isset($user['name'])) {
    $name = $user['name'];
  } else {
    $name = 'unknown';
  }
?>