Generator return values in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to yield values from the generator.

PHP

<?php
function gen() {
    yield 1;
    yield [1];
}

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

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

A2

B3

C4

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using a value that is not a number.

Forgetting to yield the second value.

The generator yields 1 first, then yields 2 as the next value.

2fill in blank

medium

Complete the code to get the return value from the generator.

PHP

<?php
function gen() {
    yield 1;
    return [1];
}

$generator = gen();
foreach ($generator as $value) {
    echo $value . " ";
}
$returnValue = $generator->getReturn();
echo "Return: " . $returnValue;
?>

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

A10

B30

C20

D40

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to get the return value before the generator finishes.

Using getReturn() without iterating the generator first.

The generator returns 20 after yielding 1. The getReturn() method retrieves this value.

3fill in blank

hard

Fix the error in the code to correctly get the generator's return value.

PHP

<?php
function gen() {
    yield 1;
    return [1];
}

$generator = gen();
foreach ($generator as $value) {}
$returnValue = $generator->getReturn();
echo "Return: " . $returnValue;
?>

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

A100

B200

C300

D400

Attempts:

3 left

💡 Hint

Common Mistakes

Calling getReturn() before iterating the generator.

Not yielding any value before returning.

The generator must be iterated before calling getReturn(). Here, the return value is 100.

4fill in blank

hard

Fill both blanks to yield values and return a final value from the generator.

PHP

<?php
function gen() {
    yield [1];
    yield [2];
    return 50;
}

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

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

A10

B20

C30

D40

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same value for both yields.

Not returning the final value.

The generator yields 10 and then 30 before returning 50.

5fill in blank

hard

Fill all three blanks to yield values and return a final value, then get the return value.

PHP

<?php
function gen() {
    yield [1];
    yield [2];
    return [3];
}

$generator = gen();
foreach ($generator as $value) {
    echo $value . " ";
}
echo "Return: " . $generator->getReturn();
?>

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

A5

B15

C25

D35

Attempts:

3 left

💡 Hint

Common Mistakes

Not calling getReturn() after iteration.

Mixing up yield and return values.

The generator yields 35 and 15, then returns 25. The return value is printed after iteration.

Practice

1. What does the return statement inside a PHP generator function do?

easy

A. It resets the generator to the beginning.

B. It immediately stops the generator and throws an error.

C. It sets the final value accessible via getReturn() after iteration.

D. It yields a value to the caller like yield does.

Solution

1. Step 1: Understand generator return behavior

   In PHP, return inside a generator does not yield a value but sets a final return value.

2. Step 2: Accessing the return value

   This final value can be accessed after iteration using the getReturn() method on the generator object.

3. Final Answer:

   It sets the final value accessible via getReturn() after iteration. -> Option C

4. Quick Check:

   Generator return sets final value = D [OK]

Hint: Remember: return in generators sets final value, not yields [OK]

Common Mistakes:

• Thinking return yields a value
• Assuming return throws an error
• Confusing return with yield

2. Which of the following is the correct syntax to get the return value of a generator after iteration?

easy

A. $gen->getReturn();

B. $gen->return();

C. $gen->yieldReturn();

D. $gen->finalValue();

Solution

1. Step 1: Identify the method to get generator return

   PHP provides getReturn() method on generator objects to retrieve the final return value after iteration.

2. Step 2: Check other options

   Other methods like return(), yieldReturn(), or finalValue() do not exist in PHP generators.

3. Final Answer:

   $gen->getReturn(); -> Option A

4. Quick Check:

   Use getReturn() to get final value [OK]

Hint: Use getReturn() method on generator object [OK]

Common Mistakes:

• Using non-existent methods like return()
• Trying to get return value before iteration
• Confusing yield with return

3. What will be the output of the following PHP code?

$gen = (function() {
    yield 1;
    yield 2;
    return 3;
})();
foreach ($gen as $value) {
    echo $value . ' ';
}
echo $gen->getReturn();

medium

A. 3

B. 1 2 3

C. 1 2

D. 1 2 0

Solution

1. Step 1: Iterate generator yields

   The generator yields 1 and 2, so the loop prints "1 2 ".

2. Step 2: Get the return value after iteration

   After the loop, getReturn() returns 3, which is printed immediately after.

3. Final Answer:

   1 2 3 -> Option B

4. Quick Check:

   Yields + return value = 1 2 3 [OK]

Hint: Print yields in loop, then append getReturn() value [OK]

Common Mistakes:

• Expecting return to yield a value
• Not calling getReturn() after iteration
• Assuming getReturn() returns 0 by default

4. Identify the error in this PHP generator code:

function gen() {
    yield 1;
    return 2;
    yield 3;
}
$g = gen();
foreach ($g as $v) {
    echo $v . ' ';
}
echo $g->getReturn();

medium

A. The yield 3; after return is unreachable code.

B. You cannot use return inside a generator.

C. The getReturn() method does not exist.

D. The generator must yield at least three values.

Solution

1. Step 1: Analyze code flow after return

   Once return 2; executes, the function ends, so yield 3; is never reached.

2. Step 2: Confirm other statements

   Using return in generators is valid, getReturn() exists, and no minimum yield count is required.

3. Final Answer:

   The yield 3; after return is unreachable code. -> Option A

4. Quick Check:

   Code after return is unreachable = B [OK]

Hint: Code after return in generator is never executed [OK]

Common Mistakes:

• Thinking yield after return runs
• Believing return is not allowed in generators
• Ignoring unreachable code warnings

5. You want to create a generator that yields numbers 1 to 3 and then returns their sum. Which code correctly achieves this?

hard

A. function gen() {
yield 1;
yield 2;
yield 3;
return 7;
}

B. function gen() {
for ($i = 1; $i <= 3; $i++) {
yield $i;
}
return $i;
}

C. function gen() {
yield 1;
yield 2;
yield 3;
return 6;
yield 7;
}

D. function gen() {
$sum = 0;
for ($i = 1; $i <= 3; $i++) {
$sum += $i;
yield $i;
}
return $sum;
}

Solution

1. Step 1: Check yielding numbers 1 to 3

   function gen() { $sum = 0; for ($i = 1; $i <= 3; $i++) { $sum += $i; yield $i; } return $sum; } uses a loop to yield 1, 2, 3 and sums them in $sum.

2. Step 2: Verify other options

   The second option yields 1-3 but returns $i (4 after loop), not sum 6. The third has unreachable yield 7; after return. The fourth returns 7, wrong sum.

3. Final Answer:

   The code that accumulates the sum during yielding -> Option D

4. Quick Check:

   Yield loop + sum return = A [OK]

Hint: Sum while yielding, then return sum after loop ends [OK]

Common Mistakes:

• Placing code after return (unreachable)
• Returning wrong sum value
• Not accumulating sum during yield