Yield from delegation in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to yield values from the generator.

PHP

<?php
function gen1() {
    yield 1;
    yield 2;
}

function gen2() {
    [1] gen1();
    yield 3;
}

foreach (gen2() as $value) {
    echo $value . " ";
}
?>

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

Ayield from

Byield

Creturn

Decho

Attempts:

3 left

💡 Hint

Common Mistakes

Using just 'yield' instead of 'yield from' will yield the generator object itself, not its values.

Using 'return' will stop the function and not yield values.

Using 'echo' is invalid syntax here.

The yield from keyword delegates yielding to another generator, allowing gen2() to yield all values from gen1() before continuing.

2fill in blank

medium

Complete the code to delegate yielding from the inner generator.

PHP

<?php
function inner() {
    yield 'a';
    yield 'b';
}

function outer() {
    [1] inner();
    yield 'c';
}

foreach (outer() as $char) {
    echo $char;
}
?>

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

Aprint

Breturn

Cyield from

Dyield

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'yield' alone yields the generator object, not its values.

Using 'return' stops the function and does not yield values.

Using 'print' is not valid syntax here.

yield from delegates yielding to the inner() generator, so outer() yields 'a', 'b', then 'c'.

3fill in blank

hard

Fix the error in the code to correctly delegate yielding.

PHP

<?php
function numbers() {
    yield 1;
    yield 2;
}

function combined() {
    [1] numbers();
    yield 3;
}

foreach (combined() as $num) {
    echo $num . ' ';
}
?>

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

Areturn

Byield from

Cyield

Decho

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'yield' alone yields the generator object, not its values.

Using 'return' stops the function prematurely.

Using 'echo' is invalid here.

Using yield from correctly delegates yielding all values from numbers() inside combined().

4fill in blank

hard

Fill both blanks to create a generator that yields squares of numbers greater than 3.

PHP

<?php
function squares() {
    return [1, 2, 3, 4, 5];
}

function filteredSquares() {
    foreach (squares() as $num) {
        if ($num [1] 3) {
            yield $num [2] 2;
        }
    }
}

foreach (filteredSquares() as $val) {
    echo $val . ' ';
}
?>

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

A>

B**

C<

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' will yield squares of numbers less than 3.

Using '+' instead of '**' will add 2 instead of squaring.

Using incorrect operators causes wrong output.

The condition $num > 3 filters numbers greater than 3, and $num ** 2 yields their squares.

5fill in blank

hard

Fill both blanks to create a generator that yields uppercase keys and values greater than 10.

PHP

<?php
function data() {
    return ['a' => 5, 'b' => 15, 'c' => 20];
}

function filteredData() {
    foreach (data() as $key => $value) {
        if ($value [1] 10) {
            yield [2] => $value;
        }
    }
}

foreach (filteredData() as $k => $v) {
    echo "$k:$v ";
}
?>

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

A>

Bstrtoupper($key)

C<

D$key

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' filters wrong values.

Yielding original key instead of uppercase key.

Mixing up operators causes wrong filtering.

The condition $value > 10 filters values greater than 10. The key is converted to uppercase with strtoupper($key).