PHP
Computing the score
Walk all questions with foreach and compute the correct count.
Quiz class and score method
To hold multiple questions in one package, you'll define a Quiz class. Its public array $questions property stores question objects in an array. The constructor takes this array and assigns it to the property.
To compute the score you add a score(array $answers): int method. This method walks all questions with a foreach loop, calls isCorrect on each, and counts the correct ones. The $answers parameter is an array of the user's answer indexes, one per question.
Counter with the accumulator pattern
Inside the score method you keep a $correct counter. It starts at $correct = 0;. As you walk each question with foreach, if the answer is correct you increment with $correct++. Finally you return the total with return $correct;.
This is the accumulator pattern: a variable is initialized, conditionally incremented inside a loop, and returned at the end. It's a common pattern for scores, averages, totals and similar calculations.
Exercise Add the Quiz class and score method
After the Question class, define a Quiz class. Add a public array $questions; property and a public function __construct(array $questions = []) constructor; inside it assign $this->questions = $questions;. Then add a public function score(array $answers): int method. Inside it initialize $correct = 0;, walk with foreach ($this->questions as $i => $q), check with if ($q->isCorrect($answers[$i] ?? -1)), and increment with $correct++ when correct. Finally return with return $correct;. Load two questions with $quiz = new Quiz([...]); and print the score with echo $quiz->score([0, 1]);.
Show example solution
int { $correct = 0; foreach ($this->questions as $i => $q) { if ($q->isCorrect($answers[$i] ?? -1)) { $correct++; } } return $correct; } }. Load two questions with $quiz = new Quiz([ new Question("What is PHP?", ["Scripting language", "Database", "Browser"], 0), new Question("Which is a loop?", ["if", "for", "echo"], 1), ]); and print with echo $quiz->score([0, 1]);.
Example solution:
<?php
// Question + Quiz classes for score calculation
class Question {
public string $text = "";
public array $options = [];
public int $answerIndex = 0;
public function __construct(string $text, array $options, int $answerIndex) {
$this->text = $text;
$this->options = $options;
$this->answerIndex = $answerIndex;
}
public function isCorrect(int $choice): bool {
return $choice === $this->answerIndex;
}
}
class Quiz {
public array $questions;
public function __construct(array $questions = []) {
$this->questions = $questions;
}
public function score(array $answers): int {
$correct = 0;
foreach ($this->questions as $i => $q) {
if ($q->isCorrect($answers[$i] ?? -1)) {
$correct++;
}
}
return $correct;
}
}
$quiz = new Quiz([
new Question("What is PHP?", ["Scripting language", "Database", "Browser"], 0),
new Question("Which is a loop?", ["if", "for", "echo"], 1),
]);
echo $quiz->score([0, 1]);
Test yourself
-
What does a foreach loop do?
- Only increments numbers by one
- Defines a class
- Reads a file
- Walks through all elements of an array in order
Show answer
Walks through all elements of an array in order — Correct. foreach walks all elements of an array in order and runs the loop body for each.
-
Complete the element part of the foreach loop
foreach ($this->questions as ____) {
if ($q->isCorrect($answers[$i] ?? -1)) {
$correct++;
}
}
Show answer
foreach ($this->questions as $i => $q) {
if ($q->isCorrect($answers[$i] ?? -1)) {
$correct++;
}
}
-
Match the score calculation concepts
- foreach
- Loop construct
- $correct
- Counter variable
- $correct++
- Increment counter
- return $correct
- Returns the total
Next lesson: Project final - Quiz app
