Iterator interface implementation in PHP - Mini Project: Build & Apply

Iterator interface implementation

📖 Scenario: You are creating a simple collection class in PHP that holds a list of fruits. You want to make this class iterable so you can loop through the fruits easily.

🎯 Goal: Build a PHP class called FruitCollection that implements the Iterator interface to allow looping over the fruits.

📋 What You'll Learn

Create a class called FruitCollection with a private array property $fruits containing exactly these fruits: 'Apple', 'Banana', 'Cherry'

Add a private integer property $position to track the current position in the iterator

Implement all required methods of the Iterator interface: current(), key(), next(), rewind(), and valid()

In the rewind() method, reset $position to 0

In the valid() method, check if the current position is valid in the $fruits array

Use a foreach loop to iterate over an instance of FruitCollection and print each fruit

💡 Why This Matters

🌍 Real World

Custom iterable classes are useful when you want to create your own collections or data structures that behave like arrays but have extra features.

💼 Career

Understanding how to implement Iterator is important for PHP developers working with custom data containers, frameworks, or libraries that require iterable objects.

1

Create the FruitCollection class with fruits array

Create a PHP class called FruitCollection with a private array property $fruits containing exactly these fruits: 'Apple', 'Banana', 'Cherry'. Also add a private integer property $position initialized to 0.

PHP

<?php

// Create class FruitCollection with private properties $fruits and $position
// Your code here

Need a hint?

Define the class and properties exactly as described. Use PHP 7.4+ typed properties.

2

Implement the rewind() and current() methods

Inside the FruitCollection class, implement the rewind() method to reset $position to 0. Also implement the current() method to return the fruit at the current $position.

PHP

<?php

class FruitCollection implements Iterator {
    private array $fruits = ['Apple', 'Banana', 'Cherry'];
    private int $position = 0;

    // Implement rewind() method
    // Your code here

    // Implement current() method
    // Your code here
}

Need a hint?

Remember rewind() resets the position. current() returns the item at the current position.

3

Implement key(), next(), and valid() methods

Inside the FruitCollection class, implement the key() method to return the current $position. Implement the next() method to increment $position by 1. Implement the valid() method to check if $position is a valid index in the $fruits array.

PHP

position = 0;
    }

    public function current(): mixed {
        return $this->fruits[$this->position];
    }

    // Implement key() method
    // Your code here

    // Implement next() method
    // Your code here

    // Implement valid() method
    // Your code here
}

Need a hint?

Use isset() in valid() to check if the position is valid.

4

Create instance and print fruits using foreach

Create an instance of FruitCollection called $fruits. Use a foreach loop to iterate over $fruits and print each fruit on its own line using echo.

PHP

position = 0;
    }

    public function current(): mixed {
        return $this->fruits[$this->position];
    }

    public function key(): int {
        return $this->position;
    }

    public function next(): void {
        $this->position++;
    }

    public function valid(): bool {
        return isset($this->fruits[$this->position]);
    }
}

// Create instance and print fruits
// Your code here

Need a hint?

Use foreach ($fruits as $fruit) and echo $fruit . "\n"; to print each fruit on a new line.