Class declaration syntax in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a class named Car.

PHP

<?php
class [1] {
}
?>

Drag options to blanks, or click blank then click option'

ACar

Bcar

Cvehicle

DCarClass

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase class names which is against convention.

Using unrelated names that don't describe the class.

The keyword class is followed by the class name, which should start with a capital letter by convention. Here, Car is the correct class name.

2fill in blank

medium

Complete the code to add a public property named $color to the class.

PHP

<?php
class Bike {
    public [1];
}
?>

Drag options to blanks, or click blank then click option'

A$speed

B$type

C$color

D$weight

Attempts:

3 left

💡 Hint

Common Mistakes

Using property names other than $color.

Forgetting the dollar sign ($) before the property name.

The property name $color matches the instruction to add a public property named $color.

3fill in blank

hard

Fix the error in the class declaration by completing the code.

PHP

<?php
[1] Vehicle {
}
?>

Drag options to blanks, or click blank then click option'

Aclass

Bfunction

Cvar

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'function' instead of 'class' for class declaration.

Omitting the 'class' keyword entirely.

The keyword class is required to declare a class in PHP. Using function or others here is incorrect.

4fill in blank

hard

Fill both blanks to declare a class named Person with a private property $name.

PHP

<?php
[1] Person {
    [2] $name;
}
?>

Drag options to blanks, or click blank then click option'

Aclass

Bpublic

Cprivate

Dfunction

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'public' instead of 'private' for the property.

Using 'function' instead of 'class' for the class declaration.

The class declaration starts with class. The property $name is declared private as requested.

5fill in blank

hard

Fill all three blanks to declare a class named Animal with a protected property $species and a public method speak().

PHP

<?php
[1] Animal {
    [2] $species;
    [3] function speak() {
        echo "Hello!";
    }
}
?>

Drag options to blanks, or click blank then click option'

Aclass

Bprotected

Cpublic

Dprivate

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong visibility keywords for properties or methods.

Forgetting to declare the class with the keyword class.

The class is declared with class. The property $species is protected to allow access in subclasses. The method speak() is public so it can be called from outside.

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