PHP
Designing a question class
Design a class that holds a question, options and the correct answer.
Setting up a question with the constructor
When you create a question, you want to supply the text, options and the correct answer together. The __construct method runs automatically when an instance is created with new, and assigns this data to properties.
The Question class constructor takes three parameters: string $text, array $options, int $answerIndex. Inside it, you copy the parameters to properties with assignments like $this->text = $text;. So new Question("What is PHP?", [...], 0) gives you a ready question.
Initializing properties with $this
Inside the constructor, the $this pseudo-variable points to the instance being created. To assign a parameter to a property you write $this->text = $text;. You repeat the same pattern for options and answerIndex.
It's good practice to declare the properties in the class first: public array $options = []; and public int $answerIndex = 0;. This makes the type and default explicit, so every instance starts in a consistent state.
Exercise Add the constructor
Add public array $options = []; and public int $answerIndex = 0; properties to the Question class. Then write a public function __construct(string $text, array $options, int $answerIndex) constructor; inside it assign $this->text = $text;, $this->options = $options;, $this->answerIndex = $answerIndex;. Update the instance to $q = new Question("What is PHP?", ["Scripting language", "Database", "Browser"], 0); and change the last line to echo count($q->options);.
Show example solution
Add public array $options = []; and public int $answerIndex = 0; to the class. Write public function __construct(string $text, array $options, int $answerIndex) { $this->text = $text; $this->options = $options; $this->answerIndex = $answerIndex; }. Create an instance with $q = new Question("What is PHP?", ["Scripting language", "Database", "Browser"], 0); and print with echo count($q->options);.
Example solution:
<?php
// Question class skeleton
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;
}
}
$q = new Question("What is PHP?", ["Scripting language", "Database", "Browser"], 0);
echo count($q->options);
Test yourself
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What data does the Question constructor take?
- Only the question text
- Question text, options and the correct answer index
- Only the number of options
- The class name and file path
Show answer
Question text, options and the correct answer index — Correct. The constructor takes the question text, the options array and the correct answer index; it assigns all three to properties.
-
Add the parameter list to the constructor
public function __construct(string ____) {
$this->text = $text;
$this->options = $options;
$this->answerIndex = $answerIndex;
}
Show answer
public function __construct(string $text, array $options, int $answerIndex) {
$this->text = $text;
$this->options = $options;
$this->answerIndex = $answerIndex;
}
-
Match the constructor concepts
- __construct
- Constructor name
- $this->text
- Property assignment
- array $options
- Options parameter
- new Question(...)
- Instantiation
Next lesson: Checking answers
