__get and __set for property access in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of __get magic method

What is the output of this PHP code when accessing the property $obj->name?

PHP

<?php
class Person {
    private $data = ['name' => 'Alice'];
    public function __get($prop) {
        return $this->data[$prop] ?? 'Unknown';
    }
}
$obj = new Person();
echo $obj->name;

A Unknown

B null

C Error: Cannot access private property

D Alice

💡 Hint

The __get method returns the value from the private array if the property exists.

The __get method intercepts access to undefined or inaccessible properties. Since 'name' exists in the private array, it returns 'Alice'.

❓ Predict Output

intermediate

Output when setting property with __set

What will be the output of this PHP code after setting $obj->age = 30; and then echoing $obj->age?

PHP

<?php
class Person {
    private $data = [];
    public function __set($prop, $value) {
        $this->data[$prop] = $value;
    }
    public function __get($prop) {
        return $this->data[$prop] ?? 'Not set';
    }
}
$obj = new Person();
$obj->age = 30;
echo $obj->age;

A 30

B Not set

C Error: Cannot access private property

D null

💡 Hint

The __set method stores the value in the private array, and __get retrieves it.

When setting $obj->age, __set stores 30 in the private array. Then __get returns 30 when accessing $obj->age.

🔧 Debug

advanced

Identify the error in __get usage

What error will this PHP code produce when trying to access $obj->city?

PHP

<?php
class Location {
    private $data = ['country' => 'USA'];
    public function __get($prop) {
        return $this->data[$prop];
    }
}
$obj = new Location();
echo $obj->city;

A Fatal error: Cannot access private property

B Notice: Undefined index: city

C null

D Unknown

💡 Hint

Accessing an undefined array key without checking causes a notice.

The __get method tries to return $this->data['city'], which does not exist, causing a PHP Notice for undefined index.

📝 Syntax

advanced

Which option causes a syntax error?

Which of the following __set method definitions will cause a syntax error in PHP?

A public function __set(string $name, mixed $value) { $this->data[$name] = $value; }

B public function __set($name, $value) { $this->data[$name] = $value; }

C public function __set($name $value) { $this->data[$name] = $value; }

D public function __set($name, $value): void { $this->data[$name] = $value; }

💡 Hint

Check the parameter list syntax carefully.

Option C misses a comma between parameters, causing a syntax error.

🚀 Application

expert

Count properties set via __set

Given this PHP class, what is the value of $obj->count after running the code below?

PHP

<?php
class Counter {
    private $data = [];
    private $count = 0;
    public function __set($name, $value) {
        $this->data[$name] = $value;
        $this->count++;
    }
    public function __get($name) {
        if ($name === 'count') {
            return $this->count;
        }
        return $this->data[$name] ?? null;
    }
}
$obj = new Counter();
$obj->a = 1;
$obj->b = 2;
$obj->a = 3;
echo $obj->count;

A 3

B Error

C 1

D 2

💡 Hint

Each __set call increments count, even if overwriting a property.

The __set method increments count every time it is called. It is called three times, so count is 3.