Why array functions matter in PHP - See It in Action

Why array functions matter

📖 Scenario: Imagine you run a small online store. You have a list of product prices, and you want to quickly find the cheapest product, the most expensive product, and the total cost of all products. Doing this manually is slow and can cause mistakes. PHP array functions help you do this easily and correctly.

🎯 Goal: You will create a PHP script that uses array functions to find the minimum price, maximum price, and total price from a list of product prices.

📋 What You'll Learn

Create an array called prices with the exact values: 15.99, 23.50, 9.99, 29.99, 12.49

Create a variable called minPrice to store the minimum price using a PHP array function

Create a variable called maxPrice to store the maximum price using a PHP array function

Create a variable called totalPrice to store the sum of all prices using a PHP array function

Print the values of minPrice, maxPrice, and totalPrice with clear labels

💡 Why This Matters

🌍 Real World

Online stores, budgeting apps, and any program that needs to analyze lists of numbers use array functions to quickly find important values.

💼 Career

Knowing how to use array functions is a basic skill for PHP developers working on web applications, data processing, and automation.

1

Create the prices array

Create an array called prices with these exact values: 15.99, 23.50, 9.99, 29.99, 12.49.

PHP

<?php

// Create the prices array with the given values
// Your code here

Hint

Use square brackets [] to create an array and separate values with commas.

2

Find the minimum, maximum, and total prices

Create a variable called minPrice and set it to the minimum value in $prices using the min() function. Then create maxPrice using max(), and totalPrice using array_sum().

PHP

<?php

$prices = [15.99, 23.50, 9.99, 29.99, 12.49];

// Use min(), max(), and array_sum() to find minPrice, maxPrice, and totalPrice
// Your code here

Hint

Use the PHP functions min(), max(), and array_sum() with the $prices array.

3

Print the results

Print the values of minPrice, maxPrice, and totalPrice each on its own line with labels: "Minimum price:", "Maximum price:", and "Total price:".

PHP

<?php

$prices = [15.99, 23.50, 9.99, 29.99, 12.49];

$minPrice = min($prices);
$maxPrice = max($prices);
$totalPrice = array_sum($prices);

// Print the results with labels
// Your code here

Hint

Use print() or echo to show the values with text labels.

4

Final check and run

Run the full PHP script to see the output showing the minimum, maximum, and total prices.

PHP

<?php

$prices = [15.99, 23.50, 9.99, 29.99, 12.49];

$minPrice = min($prices);
$maxPrice = max($prices);
$totalPrice = array_sum($prices);

print("Minimum price: $minPrice\n");
print("Maximum price: $maxPrice\n");
print("Total price: $totalPrice\n");

// Run the script to see the output
// Your code here

Hint

Make sure your script prints the correct values exactly as shown.

Practice

1. Why are PHP array functions important when working with lists?

easy

A. They make PHP run faster by changing the language core.

B. They simplify tasks like sorting and searching in arrays.

C. They allow arrays to store only numbers.

D. They prevent errors by disabling user input.

Solution

1. Step 1: Understand the role of array functions

   Array functions provide ready-made tools to handle common tasks like sorting, searching, and counting elements in arrays.

2. Step 2: Compare options

   Only They simplify tasks like sorting and searching in arrays. correctly states that array functions simplify tasks with arrays. Other options describe unrelated or incorrect effects.

3. Final Answer:

   They simplify tasks like sorting and searching in arrays. -> Option B

4. Quick Check:

   Array functions simplify array tasks = A [OK]

Hint: Remember: array functions make list tasks easier [OK]

Common Mistakes:

• Thinking array functions change PHP core speed
• Believing arrays can only hold numbers
• Confusing array functions with input validation

2. Which of the following is the correct syntax to count elements in an array $arr in PHP?

easy

A. length($arr);

B. size($arr);

C. count($arr);

D. countElements($arr);

Solution

1. Step 1: Recall PHP function for counting array elements

   The correct function to count elements in an array is count().

2. Step 2: Check each option

   Only count($arr); uses count($arr); which is valid PHP syntax. Others are not valid PHP functions.

3. Final Answer:

   count($arr); -> Option C

4. Quick Check:

   Counting array elements uses count() = B [OK]

Hint: Use count() to get array size quickly [OK]

Common Mistakes:

• Using length() which is not a PHP function
• Trying size() which doesn't exist in PHP
• Assuming countElements() is built-in

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

$numbers = [3, 1, 4, 1, 5];
sort($numbers);
print_r($numbers);

medium

A. [1, 1, 3, 4, 5]

B. Error: sort() is undefined

C. [3, 1, 4, 1, 5]

D. [5, 4, 3, 1, 1]

Solution

1. Step 1: Understand what sort() does

   The sort() function sorts the array in ascending order, changing the original array.

2. Step 2: Apply sort() to the array

   Sorting [3, 1, 4, 1, 5] ascending gives [1, 1, 3, 4, 5].

3. Final Answer:

   [1, 1, 3, 4, 5] -> Option A

4. Quick Check:

   sort() arranges numbers ascending = D [OK]

Hint: sort() arranges array ascending by default [OK]

Common Mistakes:

• Thinking sort() sorts descending by default
• Expecting original array unchanged
• Assuming sort() is not a built-in function

4. Identify the error in this PHP code snippet:

$fruits = ['apple', 'banana', 'cherry'];
$found = in_array('banana', $fruits);
if ($found = true) {
    echo 'Found banana!';
}

medium

A. Array syntax is incorrect

B. in_array() is not a valid PHP function

C. Echo statement is missing a semicolon

D. Using '=' instead of '==' in the if condition

Solution

1. Step 1: Check the if condition syntax

   The condition uses assignment '=' instead of comparison '==', so it always assigns true and evaluates as true.

2. Step 2: Correct the condition

   It should be if ($found == true) or simply if ($found) to check the boolean value.

3. Final Answer:

   Using '=' instead of '==' in the if condition -> Option D

4. Quick Check:

   Use '==' to compare, not '=' [OK]

Hint: Use '==' for comparison, '=' is assignment [OK]

Common Mistakes:

• Confusing '=' with '==' in conditions
• Thinking in_array() is invalid
• Missing semicolon after echo (actually present)

5. You have an array of user ages: $ages = [21, 17, 30, 15, 25];.
Using PHP array functions, which code snippet correctly filters out ages less than 18 and returns the filtered array?

hard

A. $adults = array_filter($ages, fn($age) => $age >= 18);

B. $adults = array_map(fn($age) => $age >= 18, $ages);

C. $adults = array_reduce($ages, fn($carry, $age) => $age >= 18 ? $age : $carry);

D. $adults = array_search(fn($age) => $age >= 18, $ages);

Solution

1. Step 1: Understand the goal

   We want to keep only ages 18 or older, so we need a function that filters elements based on a condition.

2. Step 2: Identify correct array function

   array_filter() keeps elements where the callback returns true. $adults = array_filter($ages, fn($age) => $age >= 18); uses it correctly with a function checking age >= 18.

3. Step 3: Check other options

   $adults = array_map(fn($age) => $age >= 18, $ages); uses array_map() which transforms elements but does not filter. $adults = array_reduce($ages, fn($carry, $age) => $age >= 18 ? $age : $carry); uses array_reduce() incorrectly for filtering. $adults = array_search(fn($age) => $age >= 18, $ages); uses array_search() wrongly with a callback.

4. Final Answer:

   $adults = array_filter($ages, fn($age) => $age >= 18); -> Option A

5. Quick Check:

   Use array_filter() to select elements by condition [OK]

Hint: Use array_filter() to keep elements matching condition [OK]

Common Mistakes:

• Using array_map() instead of array_filter() for filtering
• Misusing array_reduce() for filtering
• Trying to use array_search() with a callback