Named arguments in PHP - Mini Project: Build & Apply

Using Named Arguments in PHP Functions

📖 Scenario: Imagine you are creating a simple program to calculate the price of a product after applying a discount and adding tax. You want to make your function calls clear and easy to read by using named arguments.

🎯 Goal: Build a PHP program that defines a function with multiple parameters and calls it using named arguments to calculate the final price of a product.

📋 What You'll Learn

Define a function called calculatePrice with parameters price, discount, and tax.

Create variables with exact values for price, discount, and tax.

Call the calculatePrice function using named arguments in any order.

Print the final calculated price.

💡 Why This Matters

🌍 Real World

Named arguments make your code easier to read and maintain, especially when functions have many parameters or optional values.

💼 Career

Understanding named arguments helps you write clearer PHP code, which is valuable in web development jobs where code readability and maintenance are important.

1

Create variables for price, discount, and tax

Create three variables called price, discount, and tax with the exact values 100, 0.2, and 0.1 respectively.

PHP

<?php

// Create variables 'price', 'discount', and 'tax' with values 100, 0.2, and 0.1

Hint

Use the $ sign to create variables and assign the exact values given.

2

Define the calculatePrice function

Define a function called calculatePrice that takes three parameters: price, discount, and tax. The function should return the final price calculated as price - (price * discount) + (price * tax).

PHP

<?php

$price = 100;
$discount = 0.2;
$tax = 0.1;

// Define function calculatePrice with parameters price, discount, tax

Hint

Use the function keyword and return the calculation inside the function.

3

Call calculatePrice using named arguments

Call the calculatePrice function using named arguments with the variables discount, tax, and price in this exact order. Store the result in a variable called finalPrice.

PHP

<?php

$price = 100;
$discount = 0.2;
$tax = 0.1;

function calculatePrice($price, $discount, $tax) {
    return $price - ($price * $discount) + ($price * $tax);
}

// Call calculatePrice with named arguments discount, tax, price in this order

Hint

Use the syntax parameterName: value to pass named arguments in the function call.

4

Print the final price

Print the value of the variable finalPrice using echo.

PHP

<?php

$price = 100;
$discount = 0.2;
$tax = 0.1;

function calculatePrice($price, $discount, $tax) {
    return $price - ($price * $discount) + ($price * $tax);
}

$finalPrice = calculatePrice(discount: $discount, tax: $tax, price: $price);

// Print the finalPrice

Hint

Use echo $finalPrice; to display the result.

Practice

1.

What is the main benefit of using named arguments in PHP functions?

easy

A. Named arguments make functions run faster.

B. You must always provide all arguments in order.

C. You can specify arguments by name and change their order.

D. They allow you to define new functions inside existing ones.

Solution

1. Step 1: Understand named arguments concept

   Named arguments let you specify function parameters by their names instead of position.

2. Step 2: Identify the benefit

   This allows changing the order of arguments and skipping optional ones, improving readability.

3. Final Answer:

   You can specify arguments by name and change their order. -> Option C

4. Quick Check:

   Named arguments = specify by name and reorder [OK]

Hint: Named arguments let you reorder parameters by name [OK]

Common Mistakes:

• Thinking named arguments speed up execution
• Believing all arguments must be given in order
• Confusing named arguments with function definitions

2.

Which of the following is the correct syntax to call a function greet with named arguments name and age?

function greet($name, $age) { return "Hello $name, you are $age."; }

easy

A. greet("Alice", age: 30);

B. greet(name = "Alice", age = 30);

C. greet(age => 30, name => "Alice");

D. greet(name: "Alice", age: 30);

Solution

1. Step 1: Recall named argument syntax in PHP

   Named arguments use the syntax paramName: value when calling functions.

2. Step 2: Check each option

   greet(name: "Alice", age: 30); uses name: "Alice" and age: 30, which is correct syntax.

3. Final Answer:

   greet(name: "Alice", age: 30); -> Option D

4. Quick Check:

   Named argument syntax = paramName: value [OK]

Hint: Use colon : for named arguments in calls [OK]

Common Mistakes:

• Using => instead of : for named arguments
• Using = instead of : in calls
• Mixing positional and named arguments incorrectly

3.

What will be the output of the following PHP code?

function describe($color, $shape) {
    return "A $color $shape.";
}
echo describe(shape: "circle", color: "red");

medium

A. A red circle.

B. A red.

C. Syntax error.

D. A circle red.

Solution

1. Step 1: Understand named argument order

   Named arguments allow changing the order of parameters when calling the function.

2. Step 2: Substitute values in function

   Here, shape is "circle" and color is "red". The return string is "A $color $shape.", so it becomes "A red circle.".

3. Final Answer:

   A red circle. -> Option A

4. Quick Check:

   Named arguments reorder parameters = "A red circle." [OK]

Hint: Named arguments reorder parameters without error [OK]

Common Mistakes:

• Assuming order must match function definition
• Expecting syntax error from reordered named arguments
• Mixing up parameter names and values

4.

Identify the error in the following PHP code using named arguments:

function multiply($x, $y) {
    return $x * $y;
}
echo multiply(y: 5, 3);

medium

A. Function multiply is undefined.

B. Positional argument after named argument causes error.

C. Missing colon in named argument syntax.

D. No error; code runs fine.

Solution

1. Step 1: Check argument order rules

   In PHP, positional arguments must come before named arguments when calling a function.

2. Step 2: Analyze the call

   The call uses a named argument y: 5 first, then a positional argument 3, which is invalid syntax.

3. Final Answer:

   Positional argument after named argument causes error. -> Option B

4. Quick Check:

   Positional args must precede named args [OK]

Hint: Positional args must come before named args [OK]

Common Mistakes:

• Placing positional arguments after named arguments
• Forgetting colon in named argument
• Assuming named arguments can be mixed in any order

5.

Given the function below, which call correctly uses named arguments to skip the optional country parameter and specify city only?

function locationInfo(string $city, string $country = "USA") {
    return "$city, $country";
}

hard

A. locationInfo(city: "Boston");

B. locationInfo("Boston", country: "Canada");

C. locationInfo(city: "Boston", country: "Canada");

D. locationInfo(country: "Canada", city: "Boston");

Solution

1. Step 1: Understand optional parameters and named arguments

   The country parameter has a default value, so it can be skipped.

2. Step 2: Identify call that skips country and sets city

   locationInfo(city: "Boston"); calls locationInfo(city: "Boston"), skipping country and using default "USA".

3. Final Answer:

   locationInfo(city: "Boston"); -> Option A

4. Quick Check:

   Skip optional params by omitting them in named args [OK]

Hint: Skip optional params by not naming them [OK]

Common Mistakes:

• Trying to skip required parameters
• Providing positional argument after named argument
• Specifying optional parameter unnecessarily