__get and __set for property access in PHP - Step-by-Step Execution

Concept Flow - __get and __set for property access

Access property obj->prop

↓

Is property accessible?

Yes→Return property value

No↓

Call __get('prop')

↓

Return value from __get

↓

Assign obj->prop = value

↓

Is property accessible?

Yes→Set property value

No↓

Call __set('prop', value)

↓

Store value in __set

When you try to get or set a property that is not accessible, PHP calls __get or __set methods to handle it.

Execution Sample

PHP

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

This code sets and gets a property 'age' using __set and __get because 'age' is not a declared property.

Execution Table

Step	Action	Property	Value	Method Called	Result/Output
1	Assign property	age	30	__set	Stores 30 in data['age']
2	Access property	age		__get	Returns 30
3	Output				30
4	Access undefined property	name		__get	Returns 'Not set'
5	Output				Not set

💡 No more code to execute, program ends.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 4	Final
data	[]	{"age":30}	{"age":30}	{"age":30}	{"age":30}
age	undefined	30	30	30	30
name	undefined	undefined	undefined	undefined	undefined

Key Moments - 3 Insights

Why does PHP call __set when assigning to $p->age?

Because 'age' is not a declared property, PHP calls __set to handle the assignment, as shown in execution_table step 1.

Why does accessing $p->age call __get instead of returning a property directly?

Since 'age' is not declared, PHP calls __get to retrieve the value, as shown in execution_table step 2.

What happens if you access a property that was never set?

The __get method returns 'Not set' as a default, shown in execution_table step 4 and 5.

Visual Quiz - 3 Questions

Look at the execution_table, what method is called when assigning $p->age = 30?

A __set

B __get

C No method, direct assignment

D __construct

💡 Hint

Check execution_table step 1 where assignment triggers __set.

At which step does accessing an undefined property return 'Not set'?

A Step 1

B Step 2

C Step 4

D Step 3

💡 Hint

See execution_table step 4 where __get returns 'Not set'.

If the property 'age' was declared public, what would happen when assigning $p->age = 30?

A __set would still be called

B Direct assignment without __set

C __get would be called

D Error occurs

💡 Hint

Refer to concept_flow: __set is called only if property is inaccessible.

Concept Snapshot

__get and __set are magic methods in PHP.
They run when accessing or setting inaccessible properties.
__get($name) returns a value for $obj->$name.
__set($name, $value) sets a value for $obj->$name.
Use them to control dynamic property access safely.

Full Transcript

This example shows how PHP uses __get and __set when you try to get or set a property that is not declared or accessible. When you assign a value to such a property, __set is called to handle storing the value. When you read such a property, __get is called to return a value. If the property was never set, __get can return a default like 'Not set'. This lets you control how your object handles properties 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)