Array sort functions in PHP - Mini Project: Build & Apply

Array sort functions

📖 Scenario: You have a list of fruits with their prices. You want to organize this list in different ways to find the cheapest or most expensive fruits easily.

🎯 Goal: Learn how to use PHP array sort functions to sort an associative array by keys and values in ascending and descending order.

📋 What You'll Learn

Create an associative array with fruit names as keys and prices as values.

Create a variable to hold the sorted array.

Use PHP array sort functions to sort the array by values ascending and descending.

Use PHP array sort functions to sort the array by keys ascending and descending.

Print the sorted arrays to see the results.

💡 Why This Matters

🌍 Real World

Sorting arrays is useful when you want to organize data like product prices, names, or scores to find the best or worst quickly.

💼 Career

Knowing how to sort arrays is a basic skill for web developers and programmers who handle data and need to display it in a user-friendly order.

1

Create the fruits array

Create an associative array called fruits with these exact entries: 'Apple' => 3, 'Banana' => 1, 'Cherry' => 2, 'Date' => 5, 'Elderberry' => 4.

PHP

# Create the fruits array
# Your code here

Hint

Use square brackets [] to create the array and separate each fruit and price with commas.

2

Create a variable for sorted array

Create a variable called sortedFruits and set it equal to $fruits to prepare for sorting.

PHP

 3, 'Banana' => 1, 'Cherry' => 2, 'Date' => 5, 'Elderberry' => 4];

# Create a variable called sortedFruits and set it to fruits
# Your code here

Hint

Assign the existing array $fruits to a new variable $sortedFruits so you can sort it without changing the original.

3

Sort the array by values ascending

Use the PHP function asort() on $sortedFruits to sort the array by values in ascending order.

PHP

 3, 'Banana' => 1, 'Cherry' => 2, 'Date' => 5, 'Elderberry' => 4];

$sortedFruits = $fruits;

# Sort sortedFruits by values ascending
# Your code here

Hint

Use asort() to sort the array by its values while keeping the keys.

4

Print the sorted array

Print the $sortedFruits array using print_r() to display the sorted fruits by price ascending.

PHP

 3, 'Banana' => 1, 'Cherry' => 2, 'Date' => 5, 'Elderberry' => 4];

$sortedFruits = $fruits;

asort($sortedFruits);

# Print the sortedFruits array
# Your code here

Hint

Use print_r() to show the array structure and values clearly.

Practice

1. Which PHP function sorts an array and keeps the original keys intact?

easy

A. rsort()

B. sort()

C. ksort()

D. asort()

Solution

1. Step 1: Understand key preservation in sorting

   asort() sorts values but keeps the original keys unchanged.

2. Step 2: Compare with other functions

   sort() resets keys, rsort() sorts in reverse but resets keys, ksort() sorts by keys, not values.

3. Final Answer:

   asort() -> Option D

4. Quick Check:

   Keep keys while sorting values = asort() [OK]

Hint: Use asort() to sort values and keep keys unchanged [OK]

Common Mistakes:

• Confusing sort() with asort() for key preservation
• Thinking ksort() sorts by values
• Assuming rsort() keeps keys

2. Which of the following is the correct syntax to sort an array in ascending order and reset keys in PHP?

easy

A. asort($array);

B. sort($array);

C. ksort($array);

D. arsort($array);

Solution

1. Step 1: Identify function for ascending sort with key reset

   sort() sorts array values in ascending order and resets keys.

2. Step 2: Check other options

   asort() keeps keys, ksort() sorts by keys, arsort() sorts descending.

3. Final Answer:

   sort($array); -> Option B

4. Quick Check:

   Ascending sort with reset keys = sort() [OK]

Hint: Use sort() to sort ascending and reset keys [OK]

Common Mistakes:

• Using asort() when keys should reset
• Confusing ksort() with value sort
• Using arsort() for ascending order

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

$arr = [3 => 'apple', 1 => 'banana', 2 => 'cherry'];
sort($arr);
print_r($arr);

medium

A. [0 => 'apple', 1 => 'banana', 2 => 'cherry']

B. [1 => 'banana', 2 => 'cherry', 3 => 'apple']

C. [0 => 'banana', 1 => 'cherry', 2 => 'apple']

D. [0 => 'apple', 1 => 'cherry', 2 => 'banana']

Solution

1. Step 1: Understand sort() behavior on keys

   sort() sorts values ascending and resets keys starting from 0.

2. Step 2: Sort values and assign new keys

   Values sorted ascending: 'apple', 'banana', 'cherry'. Keys reset to 0,1,2 respectively.

3. Final Answer:

   [0 => 'apple', 1 => 'banana', 2 => 'cherry'] -> Option A

4. Quick Check:

   sort() resets keys and sorts ascending [OK]

Hint: sort() resets keys and sorts values ascending [OK]

Common Mistakes:

• Expecting original keys to remain
• Confusing sort() with asort()
• Mixing order of sorted values

4. Identify the error in the following PHP code snippet:

$arr = ['b' => 2, 'a' => 1, 'c' => 3];
ksort($arr, SORT_DESC);
print_r($arr);

medium

A. ksort() sorts values, not keys

B. Array keys must be numeric for ksort()

C. ksort() does not accept SORT_DESC as a parameter

D. print_r() cannot print associative arrays

Solution

1. Step 1: Check ksort() parameters

   ksort() sorts array by keys in ascending order only; it does not support descending order.

2. Step 2: Understand SORT_DESC usage

   SORT_DESC is invalid for ksort(); to sort keys descending, use krsort() instead.

3. Final Answer:

   ksort() does not accept SORT_DESC as a parameter -> Option C

4. Quick Check:

   ksort() only sorts keys ascending [OK]

Hint: Use krsort() for descending key sort, not ksort() [OK]

Common Mistakes:

• Passing SORT_DESC to ksort()
• Thinking ksort() sorts values
• Believing print_r() can't print associative arrays

5. You have an associative array with user IDs as keys and scores as values:

$scores = [101 => 50, 102 => 75, 103 => 50, 104 => 90];

You want to sort the array by scores in descending order but keep the user IDs as keys. Which function should you use?

hard

A. arsort()

B. rsort()

C. krsort()

D. sort()

Solution

1. Step 1: Identify sorting by values descending with keys preserved

   arsort() sorts array by values in descending order and keeps keys intact.

2. Step 2: Compare with other functions

   rsort() sorts values descending but resets keys, krsort() sorts keys descending, sort() sorts ascending and resets keys.

3. Final Answer:

   arsort() -> Option A

4. Quick Check:

   Sort values descending and keep keys = arsort() [OK]

Hint: Use arsort() to sort values descending and keep keys [OK]

Common Mistakes:

• Using rsort() which resets keys
• Confusing krsort() with value sort
• Using sort() which sorts ascending and resets keys