Parameters and arguments in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a parameter in PHP functions?

A parameter is a variable listed in a function's definition that acts as a placeholder for the value that will be passed to the function when it is called.

beginner

What is an argument in PHP?

An argument is the actual value or expression passed to a function when calling it, which replaces the corresponding parameter inside the function.

beginner

How do parameters and arguments relate in PHP functions?

Parameters define what inputs a function expects, while arguments are the real values given to the function when it runs, filling those parameters.

intermediate

What happens if you call a PHP function without providing all required arguments?

PHP will throw an error because the function expects certain arguments to work properly, and missing them means it cannot perform its task.

intermediate

Can PHP functions have default parameter values? What does that mean?

Yes, PHP functions can have default values for parameters. This means if no argument is passed for that parameter, the function uses the default value automatically.

In PHP, what do you call the variable inside the function definition that receives a value?

A Constant

B Argument

C Parameter

D Return value

The variable inside the function definition is called a parameter.

What is passed to a PHP function when you call it?

A Argument

B Parameter

C Function name

D Variable declaration

The actual value passed to a function when calling it is called an argument.

What happens if you call a PHP function without providing a required argument?

A The function uses a random value

B The function ignores the missing argument

C The function runs twice

D PHP throws an error

PHP throws an error because the required argument is missing.

How can you make a PHP function parameter optional?

A By giving it a default value

B By removing it from the function

C By naming it differently

D By calling the function twice

Giving a parameter a default value makes it optional.

Which of these is a correct way to define a PHP function with parameters?

A function greet(name) { echo 'Hello'; }

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

C function greet[$name] { echo 'Hello'; }

D function greet: $name { echo 'Hello'; }

In PHP, parameters use the $ sign and are inside parentheses.

Explain the difference between parameters and arguments in PHP functions.

Think about the function definition versus the function call.

Describe how default parameter values work in PHP and why they are useful.

Consider what happens if you don't pass a value for a parameter.

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