Iterator interface implementation in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start the iterator at the first element.

PHP

<?php
class MyIterator implements Iterator {
    private array $items = [1, 2, 3];
    private int $position = 0;

    public function rewind(): void {
        $this->position = [1];
    }

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

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

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

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

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

A-1

B1

C0

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Setting position to 1 skips the first element.

Using null or -1 causes errors when accessing the array.

The rewind() method resets the iterator position to the first element, which is index 0.

2fill in blank

medium

Complete the code to check if the current position is valid.

PHP

<?php
public function valid(): bool {
    return [1]($this->items[$this->position]);
}

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

Aisset

Bis_null

Carray_key_exists

Dempty

Attempts:

3 left

💡 Hint

Common Mistakes

Using empty() returns false for zero or empty strings, which may be valid elements.

Using is_null() checks value, not existence.

Using array_key_exists() requires the key, but here we check the value.

The isset() function checks if the current position exists in the array, ensuring the iterator is valid.

3fill in blank

hard

Fix the error in the next() method to correctly advance the iterator.

PHP

<?php
public function next(): void {
    $this->position [1];
}

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

A--

B-=

C+=

D++

Attempts:

3 left

💡 Hint

Common Mistakes

Using -- moves backward, causing incorrect iteration.

Using += without a value is invalid syntax.

The next() method should increase the position by one using ++ to move forward.

4fill in blank

hard

Fill both blanks to implement the current() method returning the current item.

PHP

<?php
public function current(): mixed {
    return $this->items[1];
}

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

A->position

B[$this->position]

C[position]

D($this->position)

Attempts:

3 left

💡 Hint

Common Mistakes

Using object property access ->position instead of array index.

Using parentheses instead of square brackets causes errors.

The current() method returns the element at the current position using array access syntax with [$this->position].

5fill in blank

hard

Fill all three blanks to complete the Iterator class with correct methods.

PHP

<?php
class MyIterator implements Iterator {
    private array $items = [10, 20, 30];
    private int $position = 0;

    public function rewind(): void {
        $this->position = [1];
    }

    public function current(): mixed {
        return $this->items[2];
    }

    public function valid(): bool {
        return [3]($this->items[$this->position]);
    }
}
?>

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

A0

B[$this->position]

Cisset

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting position to 1 skips the first element.

Using parentheses instead of square brackets for array access.

Using empty() or is_null() instead of isset().

The rewind() method sets position to 0, current() returns the item at current position using square brackets, and valid() checks if the position exists using isset().