__get and __set for property access in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the __get magic method in PHP?

The __get method is called when reading data from non-existing properties. It allows you to control what happens when you try to access such properties.

beginner

What does the __set magic method do in PHP?

The __set method is called when writing data to non-existing properties. It lets you define how to handle setting values to those properties.

intermediate

How do __get and __set help with property access in PHP classes?

They let you control reading and writing to non-existing properties, making your class flexible and secure by managing property access.

beginner

Show a simple example of using __get and __set in a PHP class.

class Person {
  private $data = [];
  public function __get($name) {
    return $this->data[$name] ?? null;
  }
  public function __set($name, $value) {
    $this->data[$name] = $value;
  }
}

$person = new Person();
$person->name = 'Alice';
echo $person->name; // Outputs: Alice

intermediate

What happens if you try to access a property that does not exist and __get is not defined?

PHP will trigger a notice about an undefined property and return NULL. Defining __get lets you handle this situation gracefully.

Which magic method is called when you try to read a non-existing property in PHP?

A __get

B __set

C __call

D __construct

The __get method is triggered when reading non-existing properties.

What does the __set method allow you to do?

A Control how to read properties

B Control how to write to properties

C Call methods dynamically

D Initialize the object

The __set method is called when writing to non-existing properties.

If a class has __get and __set methods, what happens when you access a non-existing property?

A __get and __set handle the access

B PHP throws a fatal error

C The property is accessed directly

D The property is ignored

__get and __set allow controlled access to non-existing properties.

What will this code output? class Test { private $data = []; public function __get($name) { return $this->data[$name] ?? 'Not set'; } public function __set($name, $value) { $this->data[$name] = $value; } } $t = new Test(); echo $t->color;

A NULL

B color

C Not set

D Error

Since 'color' is not set, __get returns 'Not set' as defined.

Why might you use __get and __set instead of public properties?

A To make code slower

B To make properties global

C To avoid writing any code

D To control and validate property access

Using __get and __set lets you control how properties are accessed and modified.

Explain how __get and __set magic methods work in PHP and why they are useful.

Think about what happens when you try to read or write a property that is not public.

Write a simple PHP class using __get and __set to store property values in a private array.

Use an array inside the class to save property values dynamically.

Practice

1.

What is the main purpose of the __get magic method in PHP?

easy

A. To control reading of inaccessible or undefined properties

B. To delete object properties

C. To initialize object properties automatically

D. To overload methods dynamically

Solution

1. Step 1: Understand the role of __get

   The __get method is called when reading a property that is inaccessible or not defined in the object.

2. Step 2: Compare with other options

   Options B, C, and D describe different behaviors unrelated to __get. Only To control reading of inaccessible or undefined properties correctly describes its purpose.

3. Final Answer:

   To control reading of inaccessible or undefined properties -> Option A

4. Quick Check:

   __get reads missing properties = A [OK]

Hint: Remember __get triggers on reading missing properties [OK]

Common Mistakes:

• Confusing __get with __set
• Thinking __get initializes properties
• Assuming __get deletes properties

2.

Which of the following is the correct syntax to define the __set magic method in a PHP class?

class Example {
    ?
}

easy

A. public function __set($name, $value) { /* code */ }

B. public function __set($value, $name) { /* code */ }

C. public function __set() { /* code */ }

D. public function set($name, $value) { /* code */ }

Solution

1. Step 1: Recall __set method signature

   The __set method must accept two parameters: the property name and the value to assign.

2. Step 2: Check parameter order and method name

   public function __set($name, $value) { /* code */ } correctly uses __set($name, $value). public function __set($value, $name) { /* code */ } reverses parameters, C has no parameters, and D uses wrong method name.

3. Final Answer:

   public function __set($name, $value) { /* code */ } -> Option A

4. Quick Check:

   __set($name, $value) correct signature = B [OK]

Hint: __set always takes property name first, then value [OK]

Common Mistakes:

• Swapping parameter order
• Omitting parameters
• Using wrong method name without double underscore

3.

What will be the output of the following PHP code?

class Test {
    private $data = [];
    public function __set($name, $value) {
        $this->data[$name] = $value;
    }
    public function __get($name) {
        return $this->data[$name] ?? 'Not found';
    }
}

$obj = new Test();
$obj->color = 'red';
echo $obj->color . ' ' . $obj->size;

medium

A. red null

B. red Not found

C. Notice error and red

D. red

Solution

1. Step 1: Understand property setting

   Setting $obj->color = 'red' calls __set, storing 'red' in $data['color'].

2. Step 2: Understand property getting

   Accessing $obj->color returns 'red'. Accessing $obj->size returns 'Not found' because $data['size'] is not set.

3. Final Answer:

   red Not found -> Option B

4. Quick Check:

   Defined property returns value, undefined returns 'Not found' = D [OK]

Hint: Undefined property returns default from __get using ?? operator [OK]

Common Mistakes:

• Expecting undefined property to be empty string
• Ignoring null coalescing operator
• Assuming Notice error on missing array key

4.

Consider this PHP class:

class Sample {
    private $props = [];
    public function __set($name, $value) {
        $this->props[$name] = $value;
    }
    public function __get($name) {
        return $this->props[$name];
    }
}

$obj = new Sample();
echo $obj->missing;

What error will occur and how to fix it?

medium

A. No error; outputs empty string

B. Fatal error; fix by declaring property publicly

C. Parse error; fix by adding return type

D. Undefined index notice; fix by using null coalescing in __get

Solution

1. Step 1: Identify error cause

   Accessing $obj->missing calls __get, which returns $this->props['missing']. Since 'missing' key is not set, PHP raises an undefined index notice.

2. Step 2: Fix the error

   Modify __get to return $this->props[$name] ?? null or a default value to avoid notice.

3. Final Answer:

   Undefined index notice; fix by using null coalescing in __get -> Option D

4. Quick Check:

   Missing key causes notice; use ?? to fix = C [OK]

Hint: Use ?? operator in __get to avoid undefined index notices [OK]

Common Mistakes:

• Ignoring undefined index notices
• Trying to declare missing properties publicly
• Confusing parse errors with runtime notices

5.

You want to create a PHP class that stores any property set dynamically and logs every property read or write. Which implementation correctly uses __get and __set to achieve this?

class Logger {
    private $data = [];
    public function __set($name, $value) {
        // ???
    }
    public function __get($name) {
        // ???
    }
}

hard

A. In __set: echo write log only; in __get: return value without logging

B. In __set: only store value; in __get: return value without logging

C. In __set: store value and echo write log; in __get: echo read log and return value or null

D. In __set: store value and return it; in __get: echo read log only

Solution

1. Step 1: Understand logging requirements

   We must log both property writes and reads, and store values dynamically.

2. Step 2: Check each option's behavior

   In __set: store value and echo write log; in __get: echo read log and return value or null stores the value in $data and echoes a write log in __set, and echoes a read log and returns the stored value or null in __get. This meets all requirements.

3. Final Answer:

   In __set: store value and echo write log; in __get: echo read log and return value or null -> Option C

4. Quick Check:

   Store and log on read/write = A [OK]

Hint: Log inside both __get and __set while storing values [OK]

Common Mistakes:

• Logging only on write or only on read
• Not returning value in __get
• Returning value in __set (which should be void)