Return values in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP function call?

Consider the following PHP code. What will be printed when foo() is called?

PHP

<?php
function foo() {
    return 5 + 3;
}
echo foo();

A Error: Undefined function foo

B 53

C 8

D 5 + 3

💡 Hint

Remember that return sends a value back from the function.

The function foo() returns the sum of 5 and 3, which is 8. The echo prints this returned value.

❓ Predict Output

intermediate

What does this function return?

Look at this PHP function. What value does it return when called with bar(4)?

PHP

<?php
function bar($x) {
    if ($x > 5) {
        return $x * 2;
    }
    return $x + 2;
}
$result = bar(4);
echo $result;

A 10

B 8

C Error: Missing return statement

D 6

💡 Hint

Check which return line runs for the input 4.

Since 4 is not greater than 5, the function returns 4 + 2 = 6.

🔧 Debug

advanced

What error does this code produce?

Examine this PHP code. What error will it cause when run?

PHP

<?php
function baz() {
    echo "Hello";
}
$result = baz();
echo $result;

A Warning: Trying to echo non-scalar value

B No error, outputs 'Hello'

C Notice: Trying to echo null value

D Notice: Undefined variable $result

💡 Hint

Consider what the function baz() returns by default.

The function baz() echoes "Hello" but does not have a return statement, so it returns null. echo $result; (null) outputs nothing and produces no error. The output is 'Hello'.

❓ Predict Output

advanced

What is the output of this recursive function?

What will this PHP code print?

PHP

<?php
function countdown($n) {
    if ($n <= 0) {
        return "Done!";
    }
    return $n . " " . countdown($n - 1);
}
echo countdown(3);

A 3 2 1 Done!

B 3 2 1

C Done! 1 2 3

D 3 2 1 0 Done!

💡 Hint

Trace the function calls and how the strings join.

The function returns a string counting down from 3 to 1, then adds 'Done!'. So the output is '3 2 1 Done!'.

🧠 Conceptual

expert

What is the value of $result after this code runs?

Consider this PHP code snippet. What is the value of $result after execution?

PHP

<?php
function test() {
    return;
    return 10;
}
$result = test();

A null

B Error: unreachable code

C 0

D 10

💡 Hint

What happens when a function returns without a value?

The first return; exits the function immediately returning null. The second return 10; is never reached.

Practice

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

easy

A. It declares a new variable inside the function.

B. It prints a value on the screen.

C. It stops the entire script immediately.

D. It sends a value back to where the function was called.

Solution

1. Step 1: Understand the purpose of return

   The return statement sends a value back to the place where the function was called.

2. Step 2: Differentiate from other actions

   It does not print or stop the whole script; it only ends the function and sends back a value.

3. Final Answer:

   It sends a value back to where the function was called. -> Option D

4. Quick Check:

   Return sends value back [OK]

Hint: Return sends value back to caller, not print or stop script [OK]

Common Mistakes:

• Thinking return prints output
• Confusing return with exit or die
• Assuming return declares variables

2. Which of the following is the correct syntax to return the value 10 from a PHP function?

easy

A. return 10;

B. return(10)

C. return = 10;

D. return: 10;

Solution

1. Step 1: Recall PHP return syntax

   The correct syntax uses the keyword return followed by the value and a semicolon: return 10;

2. Step 2: Identify syntax errors in other options

   A uses invalid assignment; return(10) misses semicolon; D uses colon incorrectly.

3. Final Answer:

   return 10; -> Option A

4. Quick Check:

   Return value ends with semicolon [OK]

Hint: Return value with semicolon, no assignment or colon [OK]

Common Mistakes:

• Omitting semicolon after return
• Using assignment operator with return
• Using colon instead of semicolon

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

function add($a, $b) {
  return $a + $b;
  echo "Done";
}
$result = add(3, 4);
echo $result;

medium

A. 7

B. Done7

C. 7Done

D. Error

Solution

1. Step 1: Understand return stops function execution

   The return $a + $b; sends back 7 and stops the function, so echo "Done"; is never run.

2. Step 2: Output the returned value

   The variable $result gets 7, and echo $result; prints 7 only.

3. Final Answer:

   7 -> Option A

4. Quick Check:

   Return stops function, only 7 printed [OK]

Hint: Code after return inside function does not run [OK]

Common Mistakes:

• Expecting code after return to execute
• Confusing echo inside function with return
• Thinking return prints output

4. Identify the error in this PHP function:

function multiply($x, $y) {
  $product = $x * $y;
  return
  $product;
}

medium

A. Missing semicolon after return

B. Return statement split incorrectly, returns nothing

C. Variable $product is undefined

D. Function missing closing brace

Solution

1. Step 1: Analyze the return statement split

   The return is on one line alone, so PHP treats it as returning nothing immediately.

2. Step 2: Understand effect of line break after return

   The next line $product; is unreachable and not part of return, causing function to return null.

3. Final Answer:

   Return statement split incorrectly, returns nothing -> Option B

4. Quick Check:

   Return must be on same line as value [OK]

Hint: Keep return and value on same line to avoid empty return [OK]

Common Mistakes:

• Splitting return and value on separate lines
• Assuming return reads next line automatically
• Ignoring PHP's automatic semicolon insertion

5. You want a PHP function that returns the first non-empty string from an array. Which function correctly returns the first non-empty string or null if none found?

hard

A. function firstNonEmpty(array $arr) {
foreach ($arr as $str) {
if ($str) {
return $str;
}
}
return '';
}

B. function firstNonEmpty(array $arr) {
foreach ($arr as $str) {
if (isset($str)) {
return $str;
}
}
return null;
}

C. function firstNonEmpty(array $arr) {
foreach ($arr as $str) {
if ($str !== '') {
return $str;
}
}
return null;
}

D. function firstNonEmpty(array $arr) {
foreach ($arr as $str) {
if ($str == '') {
return $str;
}
}
return null;
}

Solution

1. Step 1: Check condition for non-empty string

   function firstNonEmpty(array $arr) { foreach ($arr as $str) { if ($str !== '') { return $str; } } return null; } uses $str !== '' to find strings that are not empty exactly.

2. Step 2: Confirm return value if none found

   function firstNonEmpty(array $arr) { foreach ($arr as $str) { if ($str !== '') { return $str; } } return null; } returns null if no non-empty string is found, which is clear and intentional.

3. Final Answer:

   function firstNonEmpty(array $arr) { foreach ($arr as $str) { if ($str !== '') { return $str; } } return null; } -> Option C

4. Quick Check:

   Return first non-empty string or null [OK]

Hint: Use strict check !== '' to find non-empty strings [OK]

Common Mistakes:

• Using loose truthy check that skips '0' string
• Returning empty string instead of null when none found
• Returning on empty string instead of non-empty