__construct and __destruct in PHP - Step-by-Step Execution

Concept Flow - __construct and __destruct

Create Object

↓

Call __construct

↓

Use Object

↓

Object No Longer Needed

↓

Call __destruct

↓

Object Destroyed

When an object is created, __construct runs automatically to set it up. When the object is no longer needed, __destruct runs to clean up.

Execution Sample

PHP

<?php
class Demo {
  function __construct() {
    echo "Start\n";
  }
  function __destruct() {
    echo "End\n";
  }
}
$obj = new Demo();
?>

This code creates an object that prints 'Start' when made and 'End' when destroyed.

Execution Table

Step	Action	Output	Notes
1	Create object with new Demo()	Start	__construct runs and prints 'Start'
2	Object exists and can be used		No output, object ready
3	Script ends or object unset	End	__destruct runs and prints 'End'

💡 Object destroyed at script end, __destruct called

Variable Tracker

Variable	Start	After Creation	After Script Ends
$obj	undefined	object Demo instance	destroyed (no longer exists)

Key Moments - 3 Insights

Why does __construct run automatically without calling it?

__construct is a special method PHP calls automatically when you create a new object, as shown in step 1 of the execution table.

When exactly does __destruct run?

__destruct runs when the object is destroyed, usually at the end of the script or when the object is unset, as shown in step 3.

Can __destruct run multiple times for the same object?

No, __destruct runs only once when the object is destroyed, which happens once per object lifecycle.

Visual Quiz - 3 Questions

Look at the execution table, what is printed immediately after creating the object?

A Nothing

B "Start"

C "End"

D An error message

💡 Hint

Check step 1 in the execution table where __construct runs.

At which step does __destruct run according to the execution table?

A Step 3

B Step 2

C Step 1

D Never

💡 Hint

Look for when 'End' is printed in the output column.

If we unset the object before script ends, when will __destruct run?

A At script end only

B Never

C Immediately when unset is called

D Before __construct

💡 Hint

Recall __destruct runs when object is destroyed, which can happen on unset or script end.

Concept Snapshot

__construct and __destruct in PHP:
- __construct runs automatically when an object is created.
- Use __construct to initialize object properties.
- __destruct runs automatically when object is destroyed.
- Use __destruct to clean up resources.
- Both methods do not need to be called manually.

Full Transcript

In PHP, __construct is a special method that runs automatically when you create a new object. It helps set up the object, like turning on a machine when you start it. __destruct runs automatically when the object is no longer needed, like turning off the machine to save power. In the example, when we create the object, __construct prints 'Start'. When the script ends or the object is destroyed, __destruct prints 'End'. This automatic calling helps manage setup and cleanup without extra code.