Parameters and arguments in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function with default parameter

What is the output of this PHP code?

PHP

<?php
function greet($name = "Guest") {
    echo "Hello, $name!";
}
greet();
?>

A Syntax error

B Hello, !

C Hello, $name!

D Hello, Guest!

💡 Hint

Check what happens when no argument is passed to a function with a default parameter.

The function greet has a default parameter value 'Guest'. When called without arguments, it uses this default and prints 'Hello, Guest!'.

❓ Predict Output

intermediate

Output with passed argument overriding default

What will this PHP code output?

PHP

<?php
function multiply($a, $b = 2) {
    return $a * $b;
}
echo multiply(5, 3);
?>

A 6

B 15

C 10

D Error: Missing argument

💡 Hint

The second argument is provided, so default is ignored.

The function multiply multiplies $a and $b. Here, $a=5 and $b=3 (passed), so output is 15.

❓ Predict Output

advanced

Output of function with reference parameter

What is the output of this PHP code?

PHP

<?php
function addOne(&$num) {
    $num += 1;
}
$value = 10;
addOne($value);
echo $value;
?>

A 11

B 10

C 1

D Error: Cannot pass by reference

💡 Hint

The function parameter is passed by reference, so changes affect the original variable.

The function addOne increases the value of $num by 1. Since $num is passed by reference, $value changes from 10 to 11.

❓ Predict Output

advanced

Output of function with variable-length argument list

What will this PHP code output?

PHP

<?php
function sumAll(...$numbers) {
    return array_sum($numbers);
}
echo sumAll(1, 2, 3, 4);
?>

A 10

B 1,2,3,4

C Array

D Error: Unexpected ... operator

💡 Hint

The function uses a variable-length argument list to sum all numbers.

The function sumAll collects all arguments into an array and sums them. 1+2+3+4=10.

🧠 Conceptual

expert

Identify the error in function call with missing argument

What error will this PHP code produce?

PHP

<?php
function divide($x, $y) {
    return $x / $y;
}
echo divide(10);
?>

A Warning: Missing argument for parameter 2

B Output: 10

C Fatal error: Uncaught ArgumentCountError

D No error, outputs 0

💡 Hint

PHP 7+ throws a specific error when required arguments are missing.

Calling divide with only one argument causes a fatal ArgumentCountError because the second required parameter is missing.

Practice

1. What is the role of parameters in a PHP function?

easy

A. They are used to store the function's return value.

B. They are the actual values passed to the function during a call.

C. They are variables declared outside the function.

D. They are placeholders for values the function will receive when called.

Solution

1. Step 1: Understand function definition

   Parameters are the names inside the parentheses of a function definition that act as placeholders.

2. Step 2: Differentiate parameters from arguments

   Arguments are the actual values given to the function when it is called, not the placeholders.

3. Final Answer:

   They are placeholders for values the function will receive when called. -> Option D

4. Quick Check:

   Parameters = placeholders [OK]

Hint: Parameters are names in function definition, not actual values [OK]

Common Mistakes:

• Confusing parameters with arguments
• Thinking parameters hold return values
• Assuming parameters are global variables

2. Which of the following is the correct way to define a function with one parameter named name in PHP?

easy

A. function greet(name) { echo "Hello $name"; }

B. function greet(&name) { echo "Hello $name"; }

C. function greet($name) { echo "Hello $name"; }

D. function greet($name) echo "Hello $name";

Solution

1. Step 1: Check parameter syntax in PHP

   In PHP, parameters must have a $ sign before the name inside the function definition.

2. Step 2: Validate function body syntax

   The function body must be enclosed in curly braces {} to be valid.

3. Final Answer:

   function greet($name) { echo "Hello $name"; } -> Option C

4. Quick Check:

   Parameters need $ and braces [OK]

Hint: Parameters always start with $ in PHP function definitions [OK]

Common Mistakes:

• Omitting $ before parameter name
• Missing curly braces around function body
• Using & without purpose

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

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

medium

A. 7

B. 34

C. Error: Missing return statement

D. 7.0

Solution

1. Step 1: Understand function call with arguments

   The function add receives 3 and 4 as arguments for $a and $b respectively.

2. Step 2: Calculate the return value

   The function returns the sum 3 + 4 = 7, which is then printed by echo.

3. Final Answer:

   7 -> Option A

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Add numeric arguments to get sum output [OK]

Common Mistakes:

• Concatenating numbers as strings
• Expecting float output without decimals
• Thinking function lacks return

4. Identify the error in this PHP function call:

function greet($name) {
  echo "Hello, $name!";
}
greet();

medium

A. Missing argument for the parameter $name in the function call.

B. Function name is incorrect.

C. Echo statement syntax is wrong.

D. Function definition is missing curly braces.

Solution

1. Step 1: Check function parameters and call

   The function greet requires one parameter $name, but the call provides none.

2. Step 2: Understand PHP behavior on missing arguments

   Calling a function without required arguments causes an error in PHP.

3. Final Answer:

   Missing argument for the parameter $name in the function call. -> Option A

4. Quick Check:

   Required parameter missing in call [OK]

Hint: Always pass required arguments matching parameters [OK]

Common Mistakes:

• Calling function without required arguments
• Assuming default values without specifying
• Ignoring error messages about missing parameters

5. Consider this PHP function:

function multiply($x, $y = 2) {
  return $x * $y;
}

// What is the output of echo multiply(5); ?

hard

A. 5

B. 10

C. Error: Missing argument for second parameter

D. 7

Solution

1. Step 1: Identify default parameter usage

   The second parameter $y has a default value of 2, so it is optional when calling the function.

2. Step 2: Evaluate function call with one argument

   Calling multiply(5) uses 5 for $x and default 2 for $y, so returns 5 * 2 = 10.

3. Final Answer:

   10 -> Option B

4. Quick Check:

   Default parameter used, 5 * 2 = 10 [OK]

Hint: Default parameters fill missing arguments automatically [OK]

Common Mistakes:

• Expecting error when argument is missing for default parameter
• Ignoring default parameter values
• Confusing default parameter position