Class declaration syntax in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple PHP class method call

What is the output of this PHP code?

PHP

<?php
class Greeting {
    public function sayHello() {
        return "Hello, world!";
    }
}
$greet = new Greeting();
echo $greet->sayHello();
?>

A Parse error: syntax error, unexpected 'return'

B Hello, world!

C Fatal error: Call to undefined method Greeting::sayHello()

D Hello world

💡 Hint

Look at the method name and how it is called on the object.

The class Greeting has a public method sayHello() that returns the string "Hello, world!". The object $greet calls this method correctly, so the output is exactly that string.

❓ Predict Output

intermediate

Output when accessing a private property directly

What happens when this PHP code runs?

PHP

<?php
class Person {
    private string $name = "Alice";
}
$p = new Person();
echo $p->name;
?>

A Alice

B Notice: Undefined property: Person::$name

C Fatal error: Uncaught Error: Cannot access private property Person::$name

D Parse error: syntax error, unexpected 'string'

💡 Hint

Check the visibility of the property and how it is accessed.

The property $name is declared private, so it cannot be accessed directly outside the class. Trying to echo $p->name causes a fatal error about accessing a private property.

🔧 Debug

advanced

Identify the syntax error in this class declaration

This PHP code has a syntax error. Which option shows the exact error message produced when running it?

PHP

<?php
class Car {
    public $make;
    public $model
    public function __construct($make, $model) {
        $this->make = $make;
        $this->model = $model;
    }
}
?>

A Parse error: syntax error, unexpected 'public' (T_PUBLIC) in line 4

B Fatal error: Cannot redeclare class Car

C Notice: Undefined variable: model

D Parse error: syntax error, unexpected '$make' (T_VARIABLE) in line 5

💡 Hint

Look carefully at the property declarations and missing punctuation.

The property $model is missing a semicolon at the end of its declaration line, so the parser finds 'public' keyword unexpectedly on the next line, causing a syntax error.

❓ Predict Output

advanced

Output of static property access in PHP class

What is the output of this PHP code?

PHP

<?php
class Counter {
    public static int $count = 0;
    public function __construct() {
        self::$count++;
    }
}
new Counter();
new Counter();
echo Counter::$count;
?>

A 1

B 0

C Fatal error: Access to undeclared static property Counter::$count

D 2

💡 Hint

Static properties are shared across all instances of the class.

Each time a new Counter object is created, the static property $count is incremented by 1. After creating two objects, $count is 2.

❓ Predict Output

expert

Output of class constant and method call

What is the output of this PHP code?

PHP

<?php
class MathConstants {
    public const PI = 3.14;
    public static function getPi() {
        return self::PI;
    }
}
echo MathConstants::PI . ' ' . MathConstants::getPi();
?>

A 3.14 3.14

B PI 3.14

C 3.14 getPi

D Fatal error: Access to undefined constant PI

💡 Hint

Class constants are accessed with :: and can be used inside static methods with self::

The constant PI is defined as 3.14. Accessing MathConstants::PI returns 3.14. The static method getPi() returns self::PI, also 3.14. So the output is '3.14 3.14'.