Class declaration syntax in PHP - Mini Project: Build & Apply

Class declaration syntax

📖 Scenario: You are creating a simple program to represent a car using a class in PHP. This will help you understand how to declare a class and create an object.

🎯 Goal: Build a PHP class called Car with a property and a method, then create an object and display its property.

📋 What You'll Learn

Declare a class named Car

Add a public property called color with the value red

Add a public method called getColor that returns the color property

Create an object of the Car class named myCar

Print the color of myCar using the getColor method

💡 Why This Matters

🌍 Real World

Classes help organize data and behavior together, like representing real things such as cars, users, or products in a program.

💼 Career

Understanding class declaration is essential for PHP developers to build organized, reusable, and maintainable code in web applications.

1

Declare the Car class with a color property

Write a PHP class declaration named Car with a public property called color set to the string "red".

PHP

<?php

// Declare class Car with public property color set to "red"

Hint

Use the class keyword followed by the class name Car. Inside, declare a public property $color and set it to "red".

2

Add a getColor method to the Car class

Inside the Car class, add a public method called getColor that returns the value of the color property.

PHP

color
}

Hint

Define a public function named getColor inside the class. Use return $this->color; to return the property.

3

Create an object myCar of the Car class

After the Car class, create a new object named myCar using the new Car() syntax.

PHP

color;
    }
}

// Create an object myCar of class Car

Hint

Use $myCar = new Car(); to create an object from the class.

4

Print the color of myCar using getColor

Write a print statement that outputs the color of myCar by calling its getColor() method.

PHP

color;
    }
}

$myCar = new Car();

// Print the color of myCar using getColor()

Hint

Use print($myCar->getColor()); to show the color.

Practice

1. What is the correct way to start declaring a class named Car in PHP?

easy

A. class Car { }

B. function Car() { }

C. Car class { }

D. declare class Car { }

Solution

1. Step 1: Understand PHP class declaration syntax

   In PHP, classes are declared using the keyword class followed by the class name and curly braces.

2. Step 2: Match the syntax to the options

   class Car { } uses class Car { }, which is the correct syntax. Other options use incorrect keywords or order.

3. Final Answer:

   class Car { } -> Option A

4. Quick Check:

   PHP class declaration = class ClassName { } [OK]

Hint: Look for 'class' keyword followed by name and braces [OK]

Common Mistakes:

• Using 'function' instead of 'class'
• Placing 'class' after the name
• Adding extra keywords like 'declare'

2. Which of the following is the correct syntax to declare an empty class named Person in PHP?

easy

A. class Person() { }

B. class Person[] { }

C. class Person {};

D. class Person { }

Solution

1. Step 1: Recall PHP class declaration syntax

   PHP classes are declared with the keyword class, the class name, and curly braces without parentheses or brackets.

2. Step 2: Check each option

   class Person { } uses class Person { }, which is correct. class Person() { } wrongly uses parentheses, B uses brackets, and D adds a semicolon after braces which is unnecessary.

3. Final Answer:

   class Person { } -> Option D

4. Quick Check:

   Empty class = class Name { } [OK]

Hint: No parentheses or brackets after class name [OK]

Common Mistakes:

• Adding parentheses after class name
• Using square brackets after class name
• Adding unnecessary semicolon after class braces

3. What will be the output of this PHP code?

class Dog {
  public $name = "Buddy";
}
$dog = new Dog();
echo $dog->name;

medium

A. Buddy

B. Dog

C. Error: Undefined property

D. null

Solution

1. Step 1: Understand the class and property

   The class Dog has a public property $name set to "Buddy".

2. Step 2: Create an object and access property

   Creating $dog = new Dog(); makes an object. Accessing $dog->name returns "Buddy".

3. Final Answer:

   Buddy -> Option A

4. Quick Check:

   Access public property = property value [OK]

Hint: Public properties can be accessed directly via object [OK]

Common Mistakes:

• Expecting class name instead of property value
• Forgetting to create an object before access
• Assuming property is private and inaccessible

4. Identify the error in this PHP class declaration:

class Animal
  public $type;
}

medium

A. Class name should be lowercase

B. Missing opening brace { after class name

C. Property must be static

D. Missing semicolon after class name

Solution

1. Step 1: Check class declaration syntax

   PHP classes require an opening brace { immediately after the class name.

2. Step 2: Analyze the given code

   The code has no opening brace after class Animal, causing a syntax error.

3. Final Answer:

   Missing opening brace { after class name -> Option B

4. Quick Check:

   Class declaration needs { after name [OK]

Hint: Always put { right after class name [OK]

Common Mistakes:

• Omitting opening brace {
• Thinking semicolon needed after class name
• Confusing property declaration rules

5. You want to declare a PHP class Book with a property $title initialized to "PHP Basics" and a method getTitle() that returns the title. Which is the correct class declaration?

hard

A. class Book {
public $title;
public function getTitle() {
return $title;
}
}

B. class Book {
public $title = "PHP Basics";
function getTitle() {
return title;
}
}

C. class Book {
public $title = "PHP Basics";
public function getTitle() {
return $this->title;
}
}

D. class Book {
public $title = "PHP Basics";
public function getTitle() {
return $Book->title;
}
}

Solution

1. Step 1: Declare property with initial value

   Property $title is declared public and initialized to "PHP Basics" correctly in class Book { public $title = "PHP Basics"; public function getTitle() { return $this->title; } }.

2. Step 2: Define method returning property

   Method getTitle() must return $this->title to access the object's property. class Book { public $title = "PHP Basics"; public function getTitle() { return $this->title; } } does this correctly.

3. Step 3: Check other options for errors

   class Book { public $title = "PHP Basics"; function getTitle() { return title; } } returns title without $this->, class Book { public $title; public function getTitle() { return $title; } } returns $title which is undefined in method scope, class Book { public $title = "PHP Basics"; public function getTitle() { return $Book->title; } } uses $Book->title which is invalid inside class.

4. Final Answer:

   class Book { public $title = "PHP Basics"; public function getTitle() { return $this->title; } } -> Option C

5. Quick Check:

   Use $this->property inside methods [OK]

Hint: Use $this->property to access inside methods [OK]

Common Mistakes:

• Returning property without $this-> inside method
• Using variable names without $this->
• Trying to access property with class name variable