Array slice and splice in PHP - Mini Project: Build & Apply

Array slice and splice

📖 Scenario: You are managing a list of fruits in a basket. Sometimes you want to look at a part of the list without changing it, and sometimes you want to remove some fruits and add new ones in their place.

🎯 Goal: Learn how to use PHP array functions array_slice to get a part of an array without changing it, and array_splice to remove and add elements in an array.

📋 What You'll Learn

Create an array called $fruits with exact values: 'apple', 'banana', 'cherry', 'date', 'elderberry'

Create a variable called $start and set it to 1

Use array_slice with $fruits and $start to get a slice called $someFruits

Use array_splice on $fruits starting at $start to remove 2 elements and add 'fig' and 'grape'

Print $someFruits and $fruits arrays using print_r

💡 Why This Matters

🌍 Real World

Managing lists of items where you want to look at parts of the list or change parts of it, like editing a shopping list or playlist.

💼 Career

Understanding how to manipulate arrays is essential for backend development, data processing, and working with collections of data in PHP.

1

Create the initial array of fruits

Create an array called $fruits with these exact values in order: 'apple', 'banana', 'cherry', 'date', 'elderberry'.

PHP

# Your code here

Hint

Use square brackets [] to create the array with the exact fruit names as strings.

2

Set the start index for slicing and splicing

Create a variable called $start and set it to the number 1.

PHP

<?php
$fruits = ['apple', 'banana', 'cherry', 'date', 'elderberry'];
# Your code here

Hint

Just assign the number 1 to the variable $start.

3

Get a slice of the fruits array

Use array_slice with $fruits and $start to create a new array called $someFruits that contains the part of $fruits starting from index 1.

PHP

<?php
$fruits = ['apple', 'banana', 'cherry', 'date', 'elderberry'];
$start = 1;
# Your code here

Hint

Use array_slice with two arguments: the array and the start index.

4

Remove and add fruits using array_splice and print results

Use array_splice on $fruits starting at $start to remove 2 elements and add 'fig' and 'grape'. Then print $someFruits and $fruits using print_r.

PHP

<?php
$fruits = ['apple', 'banana', 'cherry', 'date', 'elderberry'];
$start = 1;
$someFruits = array_slice($fruits, $start);
# Your code here

Hint

Use array_splice with four arguments: the array, start index, number to remove, and an array of new fruits to add. Then use print_r to show both arrays.

Practice

1. What is the main difference between array_slice and array_splice in PHP?

easy

A. array_slice returns a new array without changing the original, while array_splice modifies the original array.

B. array_slice modifies the original array, while array_splice returns a new array without changes.

C. Both functions modify the original array but in different ways.

D. Both functions return a new array and do not modify the original array.

Solution

1. Step 1: Understand array_slice behavior

   array_slice extracts a portion of the array and returns it as a new array without changing the original array.

2. Step 2: Understand array_splice behavior

   array_splice removes or replaces elements in the original array and returns the removed elements, thus modifying the original array.

3. Final Answer:

   array_slice returns a new array without changing the original, while array_splice modifies the original array. -> Option A

4. Quick Check:

   Slice copies, splice changes original [OK]

Hint: Slice copies array parts, splice changes the original array [OK]

Common Mistakes:

• Thinking both functions modify the original array
• Confusing which function returns a new array
• Assuming splice returns the modified array instead of removed elements

2. Which of the following is the correct syntax to remove 2 elements starting from index 1 using array_splice on array $arr?

easy

A. array_splice($arr, 2, 1);

B. array_splice($arr, 1);

C. array_splice($arr, 1, 2);

D. array_splice($arr, 0, 2);

Solution

1. Step 1: Identify parameters of array_splice

   The function signature is array_splice(array &$array, int $offset, int $length = ?). To remove 2 elements starting at index 1, offset = 1 and length = 2.

2. Step 2: Match parameters to options

   array_splice($arr, 1, 2); uses array_splice($arr, 1, 2); which correctly removes 2 elements starting from index 1.

3. Final Answer:

   array_splice($arr, 1, 2); -> Option C

4. Quick Check:

   Offset 1, length 2 removes correct elements [OK]

Hint: array_splice($arr, start, length) removes elements from start [OK]

Common Mistakes:

• Swapping offset and length values
• Omitting length parameter and removing all after offset
• Using wrong index for offset

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

$arr = [10, 20, 30, 40, 50];
$result = array_slice($arr, 2, 2);
print_r($result);

medium

A. [30, 40]

B. [20, 30]

C. [40, 50]

D. [10, 20]

Solution

1. Step 1: Understand array_slice parameters

   It extracts elements starting at index 2, taking 2 elements from $arr.

2. Step 2: Extract elements from the array

   Index 2 is 30, next element is 40, so the slice is [30, 40].

3. Final Answer:

   [30, 40] -> Option A

4. Quick Check:

   Slice from index 2, length 2 = [30, 40] [OK]

Hint: array_slice returns a new array from offset with given length [OK]

Common Mistakes:

• Confusing index start point
• Assuming original array is changed
• Mixing up array_slice with array_splice

4. Consider this code snippet:

$arr = [1, 2, 3, 4, 5];
array_splice($arr, 2, 2, [8, 9]);
print_r($arr);

What is the output?

medium

A. [1, 2, 3, 4, 8, 9, 5]

B. [1, 2, 3, 4, 5]

C. [8, 9, 5]

D. [1, 2, 8, 9, 5]

Solution

1. Step 1: Understand array_splice with replacement

   The call removes 2 elements starting at index 2 (elements 3 and 4) and inserts [8, 9] at that position.

2. Step 2: Modify the original array accordingly

   Original array: [1, 2, 3, 4, 5]
   Remove elements at index 2 and 3: [3, 4]
   Insert [8, 9] at index 2
   Resulting array: [1, 2, 8, 9, 5]

3. Final Answer:

   [1, 2, 8, 9, 5] -> Option D

4. Quick Check:

   Splice replaces elements with new ones [OK]

Hint: Splice can replace elements by passing replacement array [OK]

Common Mistakes:

• Expecting original array unchanged
• Forgetting splice removes elements before inserting
• Confusing splice insertion with append

5. You have an array $data = [5, 10, 15, 20, 25, 30]. You want to remove the middle two elements and insert 100 and 200 in their place, then get a new array with the last three elements without changing the original array. Which code snippet correctly does this?

hard

A. array_splice($data, 2, 2, [100, 200]);
$copy = array_slice($data, -3);
print_r($copy);

B. $copy = array_slice($data, -3);
array_splice($data, 2, 2, [100, 200]);
print_r($copy);

C. $copy = array_splice($data, -3);
array_splice($data, 2, 2, [100, 200]);
print_r($copy);

D. $copy = array_slice($data, 2, 3);
array_splice($data, 2, 2, [100, 200]);
print_r($copy);

Solution

1. Step 1: Extract last three elements without changing original

   Using array_slice($data, -3) copies last three elements [20, 25, 30] into $copy without modifying $data.

2. Step 2: Modify original array by replacing middle two elements

   array_splice($data, 2, 2, [100, 200]) removes elements at index 2 and 3 (15, 20) and inserts 100 and 200.

3. Step 3: Print the copied array

   Printing $copy shows the last three elements of the original array before modification.

4. Final Answer:

   $copy = array_slice($data, -3); array_splice($data, 2, 2, [100, 200]); print_r($copy); -> Option B

5. Quick Check:

   Slice first to copy, then splice to modify [OK]

Hint: Slice first to copy, then splice to modify original [OK]

Common Mistakes:

• Using splice to copy array (modifies original)
• Modifying array before slicing (copy changes)
• Wrong slice parameters for last elements