Object instantiation with new in PHP - Step-by-Step Execution

Concept Flow - Object instantiation with new

Define Class

↓

Call new ClassName()

↓

Allocate Memory for Object

↓

Run Constructor (if any)

↓

Return Object Reference

↓

Assign to Variable

↓

Use Object

This flow shows how PHP creates a new object: it defines the class, calls new, allocates memory, runs the constructor, returns the object, and assigns it to a variable.

Execution Sample

PHP

<?php
class Car {
  public $color;
  function __construct($color) {
    $this->color = $color;
  }
}
$myCar = new Car('red');
echo $myCar->color;
?>

This code creates a Car object with color 'red' and prints the color.

Execution Table

Step	Action	Evaluation	Result
1	Define class Car	Class Car defined	Class Car available
2	Call new Car('red')	Allocate memory for new object	Memory allocated
3	Run __construct('red')	$this->color = 'red'	Object property color set to 'red'
4	Return object reference	Object created	Reference to Car object returned
5	Assign to variable $myCar	$myCar = Car object	$myCar holds reference to Car object
6	echo $myCar->color	Access property color	Output: red

💡 Execution ends after printing the color property of the object.

Variable Tracker

Variable	Start	After Step 5	Final
$myCar	undefined	Car object with color='red'	Car object with color='red'

Key Moments - 3 Insights

Why do we use 'new' to create an object?

Using 'new' tells PHP to allocate memory and run the constructor to create a fresh object, as shown in steps 2 and 3 of the execution table.

What does the constructor __construct do here?

The constructor sets the object's color property to 'red' during instantiation, as seen in step 3 where $this->color is assigned.

Why do we assign the new object to a variable?

Assigning to $myCar stores the reference so we can use the object later, shown in step 5 where $myCar holds the object.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of $myCar->color after step 5?

A undefined

B 'red'

C null

D 'blue'

💡 Hint

Check step 3 where the constructor sets color, and step 5 where $myCar is assigned.

At which step is memory allocated for the new object?

A Step 2

B Step 1

C Step 4

D Step 6

💡 Hint

Look at the action column describing memory allocation.

If we did not assign the new object to $myCar, what would happen?

A PHP would throw an error.

B The constructor would not run.

C The object would be created but immediately lost.

D The object would be stored in $myCar automatically.

💡 Hint

Refer to step 5 about assignment and variable tracking.

Concept Snapshot

Object instantiation in PHP:
Use 'new ClassName()' to create an object.
This allocates memory and runs __construct.
Assign the object to a variable to use it.
Access properties with -> operator.
Example: $obj = new ClassName();

Full Transcript

This example shows how PHP creates an object using the new keyword. First, the class Car is defined. Then, new Car('red') is called, which allocates memory for the object and runs the constructor to set the color property to 'red'. The object reference is returned and assigned to the variable $myCar. Finally, echo $myCar->color prints 'red'. This process ensures the object is properly created and ready to use.