Generator return values in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP generator code?

Consider the following PHP code using a generator with a return value. What will be the output?

PHP

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

A 1 2

B 3

C 1 2 3

D 1 2 0

💡 Hint

Remember that yield produces values one by one, and return sets the generator's return value accessible by getReturn().

The foreach loop outputs the yielded values 1 and 2. After the loop ends, getReturn() returns the value passed by return, which is 3. So the output is 1 2 3.

❓ Predict Output

intermediate

What does this PHP generator return after iteration?

What is the value returned by getReturn() after iterating this generator?

PHP

<?php
function numbers() {
    yield 10;
    yield 20;
    return 42;
}
$gen = numbers();
foreach ($gen as $num) {
    // just iterate
}
echo $gen->getReturn();

A 42

B null

C 20

D 10

💡 Hint

The return statement in a generator sets the return value accessible by getReturn().

After the generator finishes yielding values, getReturn() returns the value given by return, which is 42.

🔧 Debug

advanced

Why does this PHP code cause an error when accessing generator return value?

Examine the code below. Why does calling getReturn() cause a fatal error?

PHP

<?php
function gen() {
    yield 1;
    return 5;
}
$g = gen();
echo $g->getReturn();

A Because the generator was not fully iterated before calling getReturn()

B Because getReturn() is not a valid method for generators

C Because return values are not supported in PHP generators

D Because yield must be the last statement in the generator

💡 Hint

Think about when the generator finishes execution and when the return value is available.

The getReturn() method can only be called after the generator has finished. Since the generator was not iterated, it is not finished, so calling getReturn() causes a fatal error.

📝 Syntax

advanced

Which option correctly defines a generator with a return value in PHP?

Choose the correct PHP code snippet that defines a generator function which yields values and returns a value.

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

B function gen() { yield 1; yield 2; yield return 3; }

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

D function gen() { yield 1; yield 2; return 3; }

💡 Hint

Remember the syntax for yield and return in generators.

Option D correctly yields values then returns a value. Option D uses invalid yield return. Option D returns before yielding, so yields never run. Option D returns before second yield, so second yield is unreachable.

🚀 Application

expert

How to capture a generator's return value after partial iteration in PHP?

You have a generator that yields several values and then returns a final result. You want to iterate only the first two values and then get the return value. Which code snippet correctly achieves this?

PHP

<?php
function gen() {
    yield 'a';
    yield 'b';
    yield 'c';
    return 'done';
}
$g = gen();
// Your code here

A echo $g->getReturn(); foreach ($g as $v) {}

B $g->next(); $g->next(); foreach ($g as $v) {} echo $g->getReturn();

C foreach ($g as $v) { if ($v == 'b') break; } echo $g->getReturn();

D foreach ($g as $i => $v) { if ($i == 1) break; } echo $g->getReturn();

💡 Hint

You must fully exhaust the generator to get the return value. Breaking early leaves it unfinished.

Option B uses next() to consume the first two values ('a' and 'b'), then exhausts the generator with an empty foreach to yield the remaining value ('c'), finally retrieving the return value 'done' with getReturn(). Options B and C break after the first two values without fully exhausting the generator, causing a fatal error. Option B attempts to get the return value before iteration starts.

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