Arrow Functions and Callback Functions in PHP Practice Questions with Solutions

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Introduction

Arrow Functions and Callback Functions in PHP help you write cleaner, shorter, and reusable PHP code. Arrow functions simplify anonymous functions, while callbacks allow you to pass functions as arguments. In this chapter, you will learn both concepts through 10 practical solved PHP examples.

Question 1: Create a Simple Arrow Function to Display a Welcome Message

Problem Statement

Create an arrow function that accepts a student’s name and returns a welcome message.

PHP Solution

<?php

$welcome = fn($name) => "Welcome to PHP, " . $name;

echo $welcome("Rahul");

?>

Sample Output

Welcome to PHP, Rahul

Explanation

  • fn is the keyword used to create an arrow function.
  • $name is the function parameter.
  • The arrow function returns the welcome message automatically.
  • $welcome("Rahul") calls the function.

Concepts Covered

  • Arrow functions
  • Function parameters
  • Automatic return values

Question 2: Calculate Total Salary Using an Arrow Function

Problem Statement

Create an arrow function that accepts an employee’s basic salary and allowance and returns the total salary.

PHP Solution

<?php

$totalSalary = fn($basic, $allowance) => $basic + $allowance;

echo "Total Salary: " . $totalSalary(25000, 5000);

?>

Sample Output

Total Salary: 30000

Explanation

The arrow function accepts two parameters and adds them together. When we pass ₹25,000 as basic salary and ₹5,000 as allowance, it returns ₹30,000.

Concepts Covered

  • Multiple parameters
  • Arrow function calculations
  • Returning values

Question 3: Calculate Discounted Product Price Using an Arrow Function

Problem Statement

A shop offers a 10% discount on a product. Create an arrow function that accepts the original price and returns the discounted price.

PHP Solution

<?php

$discountPrice = fn($price) => $price - ($price * 10 / 100);

echo "Discounted Price: " . $discountPrice(2000);

?>

Sample Output

Discounted Price: 1800

Explanation

The arrow function calculates 10% of the original price and subtracts the discount from it.

For a product costing ₹2,000, the discount is ₹200. Therefore, the final price is ₹1,800.

Concepts Covered

  • Arrow functions
  • Percentage calculations
  • Returning calculated values

Question 4: Increase Product Prices Using array_map()

Problem Statement

You have an array of product prices. Use an arrow function with array_map() to increase every product price by 10%.

PHP Solution

<?php

$prices = [1000, 2000, 3000, 4000];

$updatedPrices = array_map(
    fn($price) => $price + ($price * 10 / 100),
    $prices
);

print_r($updatedPrices);

?>

Sample Output

Array
(
    [0] => 1100
    [1] => 2200
    [2] => 3300
    [3] => 4400
)

Explanation

  • array_map() applies a callback to every element.
  • The arrow function receives each product price.
  • It increases the price by 10%.
  • The updated prices are stored in a new array.

Concepts Covered

  • Arrow functions
  • Callback functions
  • array_map()
  • Array transformation

Question 5: Filter Passing Students Using array_filter()

Problem Statement

You have an array of student marks. Use an arrow function with array_filter() to display only students who scored 40 or more marks.

PHP Solution

<?php

$marks = [85, 32, 67, 25, 90, 45];

$passedStudents = array_filter(
    $marks,
    fn($mark) => $mark >= 40
);

print_r($passedStudents);

?>

Sample Output

Array
(
    [0] => 85
    [2] => 67
    [4] => 90
    [5] => 45
)

Explanation

  • array_filter() checks each array element using a callback.
  • The arrow function checks whether each mark is at least 40.
  • Only matching marks are included in the result.
  • Original array keys are preserved.

Concepts Covered

  • Arrow functions
  • Callback functions
  • array_filter()
  • Array filtering

Question 6: Sort Product Prices Using a Callback Function

Problem Statement

You have an array of product prices. Use usort() with an arrow function callback to sort the prices from lowest to highest.

PHP Solution

<?php

$prices = [4500, 1200, 3500, 800, 2500];

usort($prices, fn($a, $b) => $a <=> $b);

print_r($prices);

?>

Sample Output

Array
(
    [0] => 800
    [1] => 1200
    [2] => 2500
    [3] => 3500
    [4] => 4500
)

Explanation

  • usort() sorts an array using a custom comparison callback.
  • The arrow function compares two values at a time.
  • The spaceship operator (<=>) returns a comparison result.
  • The array is sorted in ascending order.
  • usort() reindexes the array keys.

Concepts Covered

  • Callback functions
  • Arrow functions
  • usort()
  • Spaceship operator

Question 7: Create a Custom Function That Accepts a Callback

Problem Statement

Create a function named calculateResult() that accepts two numbers and a callback function. Use the callback to calculate their sum.

PHP Solution

<?php

function calculateResult($a, $b, $callback) {
    return $callback($a, $b);
}

$result = calculateResult(
    20,
    30,
    fn($x, $y) => $x + $y
);

echo "Result: " . $result;

?>

Sample Output

Result: 50

Explanation

  • calculateResult() accepts two numbers and a callback.
  • The callback is received through the $callback parameter.
  • $callback($a, $b) executes the supplied function.
  • The arrow function adds the two numbers and returns the result.

Concepts Covered

  • Custom callback functions
  • Arrow functions
  • Passing functions as arguments
  • Function execution

Question 8: Use a Named Function as a Callback

Problem Statement

Create a named function called calculateSquare() that returns the square of a number. Pass this function to array_map() to calculate the square of every number in an array.

PHP Solution

<?php

function calculateSquare($number) {
    return $number * $number;
}

$numbers = [2, 4, 6, 8];

$squares = array_map("calculateSquare", $numbers);

print_r($squares);

?>

Sample Output

Array
(
    [0] => 4
    [1] => 16
    [2] => 36
    [3] => 64
)

Explanation

  • calculateSquare() is a named function.
  • Its name is passed to array_map() as a callback.
  • array_map() calls this function for every array element.
  • The returned square values are stored in $squares.

Concepts Covered

  • Named functions
  • Callback functions
  • array_map()
  • Array transformation

Question 9: Calculate Employee Bonuses Using an Arrow Function

Problem Statement

An organization gives employees a bonus equal to 10% of their salary. Use an arrow function with array_map() to calculate the bonus for every employee.

PHP Solution

<?php

$employees = [
    ["name" => "Rahul", "salary" => 30000],
    ["name" => "Priya", "salary" => 40000],
    ["name" => "Amit", "salary" => 50000]
];

$employeeBonuses = array_map(
    fn($employee) => [
        "name" => $employee["name"],
        "salary" => $employee["salary"],
        "bonus" => $employee["salary"] * 10 / 100
    ],
    $employees
);

print_r($employeeBonuses);

?>

Sample Output

Array
(
    [0] => Array
        (
            [name] => Rahul
            [salary] => 30000
            [bonus] => 3000
        )

    [1] => Array
        (
            [name] => Priya
            [salary] => 40000
            [bonus] => 4000
        )

    [2] => Array
        (
            [name] => Amit
            [salary] => 50000
            [bonus] => 5000
        )
)

Explanation

  • The $employees array stores employee names and salaries.
  • array_map() processes each employee record.
  • The arrow function calculates 10% of the employee’s salary.
  • It returns a new array containing the employee name, salary, and bonus.

Concepts Covered

  • Arrow functions
  • Callback functions
  • Multidimensional arrays
  • array_map()
  • Employee bonus calculations

Question 10: Build an Employee Salary Report Using Arrow and Callback Functions

Problem Statement

You have employee salary records. Increase each employee’s salary by ₹5,000 using an arrow function and array_map(). Then use array_filter() with another arrow function to display only employees whose updated salary is ₹35,000 or more.

PHP Solution

<?php

$employees = [
    ["name" => "Rahul", "salary" => 25000],
    ["name" => "Priya", "salary" => 32000],
    ["name" => "Amit", "salary" => 40000],
    ["name" => "Neha", "salary" => 28000]
];

$updatedEmployees = array_map(
    fn($employee) => [
        "name" => $employee["name"],
        "salary" => $employee["salary"] + 5000
    ],
    $employees
);

$selectedEmployees = array_filter(
    $updatedEmployees,
    fn($employee) => $employee["salary"] >= 35000
);

print_r($selectedEmployees);

?>

Sample Output

Array
(
    [1] => Array
        (
            [name] => Priya
            [salary] => 37000
        )

    [2] => Array
        (
            [name] => Amit
            [salary] => 45000
        )
)

Explanation

  • The $employees array stores the original employee records.
  • array_map() increases every employee’s salary by ₹5,000.
  • The updated records are stored in $updatedEmployees.
  • array_filter() checks the updated salary of each employee.
  • Only employees earning ₹35,000 or more are included in the final report.
  • Original array keys are preserved by array_filter().

Concepts Covered

  • Arrow functions
  • Callback functions
  • array_map()
  • array_filter()
  • Multidimensional arrays
  • Employee salary reports

Key Takeaways

  • Arrow functions provide a shorter way to write anonymous functions.
  • Arrow functions use the fn keyword.
  • Arrow functions automatically capture variables from the parent scope by value.
  • Arrow functions contain a single expression and return its result automatically.
  • Callback functions allow one function to be passed into another function.
  • Named functions and anonymous functions can both be used as callbacks.
  • array_map() applies a callback to array elements.
  • array_filter() selects array elements based on a callback condition.
  • usort() uses a callback to define custom sorting rules.
  • Custom PHP functions can also accept callbacks as arguments.

Frequently Asked Questions (FAQs)

1. What is an arrow function in PHP?

An arrow function is a shorter way to write an anonymous function using the fn keyword. It automatically returns the result of its single expression.

2. What is the syntax of an arrow function in PHP?

fn($parameter) => expression;

3. What is a callback function in PHP?

A callback is a function passed as an argument to another function so that it can be executed when needed.

4. What is the difference between arrow functions and anonymous functions?

Arrow functions use the fn keyword and automatically capture variables from the parent scope by value. Traditional anonymous functions use the function keyword and can capture variables explicitly using use.

5. Can arrow functions accept multiple parameters?

Yes. Arrow functions can accept multiple parameters.

$add = fn($a, $b) => $a + $b;

echo $add(10, 20);

Output:

30

6. Can arrow functions use variables from outside their scope?

Yes. Arrow functions automatically capture variables from the parent scope by value.

7. Can arrow functions be used with array_map()?

Yes. Arrow functions can be passed to array_map() to perform operations on every element of an array.

8. Can arrow functions be used with array_filter()?

Yes. They can be used with array_filter() to select array elements that satisfy a condition.

9. Can a named function be used as a callback?

Yes. You can pass the function name as a string or callable to another function.

10. Which PHP version supports arrow functions?

Arrow functions were introduced in PHP 7.4. You need PHP 7.4 or later to use them.

Written by Shubhranshu Shekhar, who has trained 20000+ students in coding.

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