Opereta ya Uchimbaji Salama katika OOP katika PHP

Opereta ya uchimbaji salama ?-> inaruhusu kufikia kwa usalama mbinu na sifa za vitu ambavyo vinaweza kuwa null.

Tuangalie kwa mfano. Tuchukulie tuna darasa lifuatalo:

php<?php
  class User
  {
    public $name;
    
    public function __construct($name)
    {
      $this->name = $name;
    }
  }
?>

Tutengeneze kitu cha darasa hili:

php<?php
  $user = new User('john');
?>

Tutoe thamani ya sifa yake:

php<?php
  $user = new User('john');
  echo $user->name;
?>

Tuchukulie sasa imetokea hivyo, kwamba badala ya kitu tunakuwa na null. Katika hali hii jaribio la kufikia jina la mtumiaji litasababisha hitilafu:

php<?php
  $user = null;
  echo $user->name; // hitilafu
?>

Ili kuzuia hitilafu, tunaweza kutumia opereta ya uchimbaji salama:

php<?php
  $user = null;
  echo $user?->name;
?>

php<?php
  class Employee {
    public $name;
    public $salary;
    
    public function __construct($name, $salary)
    {
      $this->name = $name;
      $this->salary = $salary;
    }
  }
  
  $employee = new Employee('john', 1000);
  
  echo $employee->name;
  echo $employee->salary;
?>