PHP
Slicing with array_slice()
Learn to take a portion of an array with array_slice().
Slicing with array_slice()
array_slice() takes a portion of an array. It has two main parameters: offset (where to start) and length (how many elements to take).
For example, array_slice([10, 20, 30, 40, 50], 1, 2) starts at index 1 and takes 2 elements; the result is [20, 30]. The original array is not changed; a new array is returned. A negative offset counts from the end: -1 gives the last element.
Negative offset and length
In array_slice(), both offset and length can be negative. A negative offset counts from the end: -2 starts at the second-to-last element. A negative length leaves that many elements off the end.
For example, array_slice([1, 2, 3, 4, 5], -2) returns [4, 5]; array_slice([1, 2, 3, 4, 5], 0, -1) drops the last element and returns [1, 2, 3, 4]. If length is omitted, it goes to the end.
Exercise Take the first three and print them
Define $nums = [10, 20, 30, 40, 50, 60]. Assign the first three elements to $first with array_slice($nums, 0, 3). Then loop with foreach ($first as $n) and print each element with echo $n . "\n".
Show example solution
First take with $first = array_slice($nums, 0, 3);. Then loop with foreach ($first as $n) { echo $n . "\n"; } and print.
Example solution:
<?php
$nums = [10, 20, 30, 40, 50, 60];
// Take the first three and print them
$first = array_slice($nums, 0, 3);
foreach ($first as $n) {
echo $n . "\n";
}
Test yourself
-
What is the output of the code below?
$arr = [1, 2, 3, 4, 5];
print_r(array_slice($arr, 2, 2));
- [1, 2]
- [2, 3]
- [3, 4]
- [1, 2, 3]
Show answer
[3, 4] — Correct. Starting at index 2 (the 3) and taking 2 elements; the result is [3, 4].
-
Complete the call to take the last two
$arr = [1, 2, 3, 4, 5];
$slice = array_slice($arr, ____);
print_r($slice);
Show answer
$arr = [1, 2, 3, 4, 5];
$slice = array_slice($arr, -2);
print_r($slice);
-
Match each parameter to its behavior
- offset = 1
- Starts at index 1
- length = 2
- Takes 2 elements
- offset = -1
- Starts at last element
Next lesson: in_array() and array_search()
