Associative Arrays in PHP Practice Questions with Solutions

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Introduction

Associative arrays in PHP store multiple values using named keys instead of numeric indexes. They make it easy to manage structured data such as employee details, student records, and product information. In this tutorial, you will learn to create, access, update, add, remove, and sort associative array elements through practical PHP examples.

Question 1: Create an Associative Array of Employee Details

Problem Statement

Create an associative array containing an employee’s ID, name, department, and salary. Display all employee details using print_r().

PHP Solution

<?php
$employee = [
    "id" => 101,
    "name" => "Rahul",
    "department" => "IT",
    "salary" => 45000
];

print_r($employee);
?>

Sample Output

Array
(
    [id] => 101
    [name] => Rahul
    [department] => IT
    [salary] => 45000
)

Explanation

  • $employee stores employee information.
  • Each value is associated with a named key.
  • "id" is a key, and 101 is its value.
  • print_r() displays all keys and values.

Concepts Covered

  • Associative array creation
  • Key-value pairs
  • print_r() function

Question 2: Access Values Using Associative Array Keys

Problem Statement

Create an associative array containing student details. Display the student’s name, course, and marks using their keys.

PHP Solution

<?php
$student = [
    "roll_no" => 25,
    "name" => "Priya",
    "course" => "PHP",
    "marks" => 92
];

echo "Student Name: " . $student["name"] . "\n";
echo "Course: " . $student["course"] . "\n";
echo "Marks: " . $student["marks"];
?>

Sample Output

Student Name: Priya
Course: PHP
Marks: 92

Explanation

  • $student["name"] accesses the student’s name.
  • $student["course"] accesses the course.
  • $student["marks"] accesses the marks.
  • Associative arrays use named keys instead of numeric positions.

Concepts Covered

  • Accessing array values
  • Associative array keys
  • Array element retrieval

Question 3: Update Values in an Associative Array

Problem Statement

Create an associative array containing employee details. Update the employee’s department from Sales to Marketing and salary from ₹35,000 to ₹42,000.

PHP Solution

<?php
$employee = [
    "id" => 102,
    "name" => "Amit",
    "department" => "Sales",
    "salary" => 35000
];

$employee["department"] = "Marketing";
$employee["salary"] = 42000;

print_r($employee);
?>

Sample Output

Array
(
    [id] => 102
    [name] => Amit
    [department] => Marketing
    [salary] => 42000
)

Explanation

  • $employee["department"] refers to the department value.
  • Assigning "Marketing" replaces the previous department.
  • $employee["salary"] updates the employee’s salary.
  • Other key-value pairs remain unchanged.

Concepts Covered

  • Updating associative array values
  • Key-based assignment
  • Modifying array elements

Question 4: Add New Elements to an Associative Array

Problem Statement

Create an associative array containing product ID, product name, and price. Add two new elements: category and stock quantity.

PHP Solution

<?php
$product = [
    "product_id" => 501,
    "product_name" => "Laptop",
    "price" => 55000
];

$product["category"] = "Electronics";
$product["stock"] = 15;

print_r($product);
?>

Sample Output

Array
(
    [product_id] => 501
    [product_name] => Laptop
    [price] => 55000
    [category] => Electronics
    [stock] => 15
)

Explanation

  • The original array contains three elements.
  • $product["category"] adds a new key-value pair.
  • $product["stock"] adds another element.
  • PHP automatically stores each new value with its specified key.

Concepts Covered

  • Adding associative array elements
  • Named keys
  • Key-value assignment

Question 5: Remove an Element Using unset()

Problem Statement

Create an associative array containing customer details. Remove the customer’s email address using unset() and display the remaining information.

PHP Solution

<?php
$customer = [
    "customer_id" => 201,
    "name" => "Neha",
    "email" => "neha@example.com",
    "city" => "Delhi",
    "phone" => "9876543210"
];

unset($customer["email"]);

print_r($customer);
?>

Sample Output

Array
(
    [customer_id] => 201
    [name] => Neha
    [city] => Delhi
    [phone] => 9876543210
)

Explanation

  • unset() removes the specified array element.
  • $customer["email"] identifies the email key.
  • The email address is removed from the array.
  • All other customer details remain available.

Concepts Covered

  • Removing associative array elements
  • unset() function
  • Key-based element deletion

Question 6: Display Associative Array Using foreach

Problem Statement

Create an associative array containing five department names and their monthly budgets. Display each department with its budget using a foreach loop.

PHP Solution

<?php
$budgets = [
    "HR" => 50000,
    "Sales" => 120000,
    "IT" => 150000,
    "Marketing" => 80000,
    "Finance" => 70000
];

foreach ($budgets as $department => $budget) {
    echo $department . " Budget: ₹" . $budget . "\n";
}
?>

Sample Output

HR Budget: ₹50000
Sales Budget: ₹120000
IT Budget: ₹150000
Marketing Budget: ₹80000
Finance Budget: ₹70000

Explanation

  • $budgets stores department names as keys.
  • Each department has a corresponding budget.
  • foreach accesses every key-value pair.
  • $department stores the current key.
  • $budget stores the corresponding value.

Concepts Covered

  • Associative array traversal
  • foreach loop
  • Key-value iteration

Question 7: Check Whether a Key Exists Using array_key_exists()

Problem Statement

Create an associative array containing employee details. Check whether the salary and bonus keys exist in the array using array_key_exists().

PHP Solution

<?php
$employee = [
    "id" => 103,
    "name" => "Rohit",
    "department" => "HR",
    "salary" => 40000
];

if (array_key_exists("salary", $employee)) {
    echo "Salary key exists.\n";
} else {
    echo "Salary key does not exist.\n";
}

if (array_key_exists("bonus", $employee)) {
    echo "Bonus key exists.";
} else {
    echo "Bonus key does not exist.";
}
?>

Sample Output

Salary key exists.
Bonus key does not exist.

Explanation

  • array_key_exists() checks whether a specified key is present.
  • The first condition checks the salary key.
  • The second condition checks the bonus key.
  • The function returns true if the key exists, even if its value is null.

Concepts Covered

  • array_key_exists() function
  • Checking array keys
  • Conditional statements

Question 8: Get All Keys and Values from an Associative Array

Problem Statement

Create an associative array containing product details. Display all keys using array_keys() and all values using array_values().

PHP Solution

<?php
$product = [
    "id" => 301,
    "name" => "Keyboard",
    "price" => 1200,
    "stock" => 25
];

$keys = array_keys($product);
$values = array_values($product);

echo "Product Keys:\n";
print_r($keys);

echo "Product Values:\n";
print_r($values);
?>

Sample Output

Product Keys:
Array
(
    [0] => id
    [1] => name
    [2] => price
    [3] => stock
)

Product Values:
Array
(
    [0] => 301
    [1] => Keyboard
    [2] => 1200
    [3] => 25
)

Explanation

  • array_keys() returns all keys from an associative array.
  • array_values() returns all values.
  • Both functions create new indexed arrays.
  • The original associative array remains unchanged.

Concepts Covered

  • array_keys() function
  • array_values() function
  • Extracting keys and values

Question 9: Calculate Total Salary Using an Associative Array

Problem Statement

Create an associative array containing five employees and their monthly salaries. Calculate the total salary expense using a foreach loop.

PHP Solution

<?php
$salaries = [
    "Rahul" => 35000,
    "Priya" => 42000,
    "Amit" => 38000,
    "Neha" => 45000,
    "Rohit" => 40000
];

$totalSalary = 0;

foreach ($salaries as $name => $salary) {
    $totalSalary += $salary;
}

echo "Total Monthly Salary: ₹" . number_format($totalSalary);
?>

Sample Output

Total Monthly Salary: ₹200,000

Explanation

  • Employee names are used as array keys.
  • Their monthly salaries are stored as values.
  • $totalSalary starts from 0.
  • The foreach loop accesses every salary.
  • Each salary is added to the total.
  • number_format() displays the total with thousands separators.

Concepts Covered

  • Associative arrays with numeric values
  • foreach loop
  • Total calculation
  • number_format() function

Question 10: Sort an Associative Array by Values Using asort()

Problem Statement

Create an associative array containing employee names and their performance scores. Sort the array in ascending order according to scores while preserving employee names as keys.

PHP Solution

<?php
$scores = [
    "Rahul" => 85,
    "Priya" => 95,
    "Amit" => 78,
    "Neha" => 90,
    "Rohit" => 82
];

asort($scores);

foreach ($scores as $name => $score) {
    echo $name . ": " . $score . "\n";
}
?>

Sample Output

Amit: 78
Rohit: 82
Rahul: 85
Neha: 90
Priya: 95

Explanation

  • $scores stores employee names as keys and scores as values.
  • asort() sorts the array by values in ascending order.
  • Employee names remain associated with their original scores.
  • The foreach loop displays the sorted results.

Concepts Covered

  • asort() function
  • Sorting associative arrays by values
  • Preserving array keys
  • foreach loop

Key Takeaways

  • Associative arrays store data using named keys and values.
  • Use the => operator to create key-value pairs.
  • Access values using $array["key"].
  • Update existing values by assigning a new value to their keys.
  • Add new elements by specifying new keys.
  • Use unset() to remove elements.
  • Use foreach to access keys and values together.
  • Use array_key_exists() to check whether a key exists.
  • Use array_keys() and array_values() to extract keys and values.
  • Use asort() to sort an associative array by values while preserving keys.

Frequently Asked Questions (FAQs)

1. What is an associative array in PHP?

An associative array is an array that uses named keys instead of automatically assigned numeric indexes. Each key is connected to a value.

2. How do you create an associative array in PHP?

Use the key => value format inside square brackets.

$student = [
    "name" => "Rahul",
    "age" => 20,
    "course" => "PHP"
];

3. How do you access an associative array value?

Use the key inside square brackets.

echo $student["name"];

Output: Rahul

4. Can we use numbers as keys in associative arrays?

Yes. PHP allows integer and string keys in arrays. However, associative arrays commonly use meaningful string keys.

5. How do you add a new key-value pair?

Assign a value to a new key.

$student["city"] = "Delhi";

6. How do you update an associative array value?

Assign a new value to an existing key.

$student["age"] = 21;

7. What is the difference between isset() and array_key_exists()?

isset() returns false when a key is missing or its value is null. array_key_exists() returns true if the key exists, even when its value is null.

8. Which loop is commonly used with associative arrays?

The foreach loop is commonly used because it can access both the key and its corresponding value.

foreach ($student as $key => $value) {
    echo $key . ": " . $value . "\n";
}

9. How do you sort an associative array by values?

Use asort() for ascending order or arsort() for descending order. Both preserve the association between keys and values.

10. Can an associative array contain different data types?

Yes. An associative array can store strings, integers, floats, Boolean values, and even other arrays.

$employee = [
    "name" => "Priya",
    "salary" => 45000,
    "active" => true
];

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

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