Aim

To implement the PHP array functions array_pad(), array_slice() and array_splice() together with list() destructuring, displaying every result with foreach wherever applicable.

Theory

PHP arrays are ordered maps, and the standard library manipulates them through value-returning and in-place functions — knowing which is which is the heart of this practical:

• array_pad($array, $size, $value) returns a copy grown to $size elements by appending $value as many times as needed. A negative size pads at the front instead, and if the array already has at least |$size| elements it is returned unchanged — the function never truncates.
• array_slice($array, $offset, $length) extracts a contiguous window without modifying the source — it is a pure read. A negative $offset counts from the end, and numeric keys are re-indexed from 0 unless the fourth argument preserve_keys is true.
• array_splice(&$array, $offset, $length, $replacement) is the destructive sibling: the array is passed by reference, the selected segment is removed and returned, and the $replacement elements are stitched into the gap (the replacement may be shorter or longer than what was removed, so the array can shrink or grow). Numeric keys are renumbered afterwards.
• list($a, $b, $c) = $array (short form [$a, $b, $c] = $array) destructures an array into individual variables in one statement — the same mechanism P6 used for swapping. Elements can be skipped with empty slots, and since PHP 7.1 keyed destructuring ["x" => $x] works too.

The mnemonic examiners love: slice reads, splice edits.

Requirements

• XAMPP/WAMP with PHP 8.x, or PHP CLI
• Code editor (VS Code); browser or terminal

Procedure

1. Start Apache from the XAMPP Control Panel.
2. Save the snippet as p07_array_functions.php in C:\xampp\htdocs\wbplab.
3. Run http://localhost/wbplab/p07_array_functions.php or php p07_array_functions.php.
4. After the first run, print_r($subjects) at the end to prove array_pad/array_slice left it untouched, then print_r($spliceSource) to prove array_splice mutated it.
5. Try array_pad($subjects, -6, "N/A") and a negative slice offset, predicting each result first.

Explanation of the Code

• $subjects = ["PHP", "HTML", "CSS"] is the base array. array_pad($subjects, 6, "N/A") returns a six-element copy in $padded — the three originals plus three "N/A" fillers; $subjects itself is untouched.
• array_slice($padded, 1, 3) copies three elements starting at index 1 into $sliced: HTML, CSS and the first N/A.
• $spliceSource = ["A", "B", "C", "D", "E"]; array_splice($spliceSource, 2, 2, ["X", "Y"]) removes two elements at index 2 (C, D) — those come back as the return value in $removed — and inserts X, Y in their place, mutating $spliceSource to A, B, X, Y, E.
• list($first, $second, $third) = $subjects; unpacks the original array into three scalars.
• Four foreach loops print each result one value per line; the final echo interpolates the three destructured variables.

Expected Output

The script prints five labelled blocks: array_pad result lists PHP, HTML, CSS, N/A, N/A, N/A (one per line); array_slice result lists HTML, CSS, N/A; array_splice removed lists C, D; array_splice updated source lists A, B, X, Y, E; and the last line reads list() values: PHP, HTML, CSS.

🎯 Viva Questions

1. Does array_pad() ever shorten an array? No — if the array already has at least the requested size it is returned unchanged.
2. How do you pad at the beginning instead of the end? Pass a negative size: array_pad($arr, -6, "N/A").
3. Key difference between array_slice() and array_splice()? Slice returns a copy and leaves the source alone; splice takes the array by reference, removes a segment and edits in place.
4. What does array_splice() return? An array containing exactly the elements it removed.
5. Can the replacement in array_splice() differ in length from the removed part? Yes — the array grows or shrinks accordingly, then numeric keys are renumbered.
6. What is the short-syntax equivalent of list()? Square-bracket destructuring: [$first, $second, $third] = $subjects; (PHP 7.1+).

CO Mapping

CO1, CO2