基本的PHP面向對象的實例化和依賴注入

Question

我試圖學習使用依賴注入，但是在使用時遇到問題。我明白這裏兩個班的情況，但是當我去使用他們時，我做錯了什麼。

class Author 
{ 
private $firstname; 
private $lastname; 

public function __construct($firstname, $lastname) 
{ 
    $this->firstName = $firstName; 
    $this->lastName = $lastName; 
} 

public function getFirstName() 
{ 
    return $this->firstName; 
} 

public function getLastName() 
{ 
    return $this->lastName; 
} 
} 

class Question 
{ 
private $author; 
private $question; 

public function __construct($question, Author $author) 
{ 
    $this->author = $author; 
    $this->question = $question; 
} 

public function getAuthor() 
{ 
    return $this->author; 
} 

public function getQuestion() 
{ 
    return $this->question; 
} 
} 

好吧有兩個基本的類使用依賴注入。我明白這一切，但如果我想使用它們。我試過這個，我得到一個錯誤。

$author = new Author('Mickey', 'Mouse'); 
$author->getFirstName(); 

$question = new Question('what day is it?', $author); 
$question->getQuestion(); 

我希望它輸出「米奇」和「今天是哪天？」，但我得到以下錯誤。

Undefined variable: firstName in /var/www/OOP/dependency-injection/example1.php on line 12 
Undefined variable: lastName in /var/www/OOP/dependency-injection/example1.php on line 13 

爲什麼我得到這個錯誤？我以爲我在這裏宣佈了變數$author = new Author('Mickey', 'Mouse');？

感謝您的任何見解。

Answer 1

您firstname和firstName不要在您Author類匹配

public function __construct($firstname, $lastname) 
{ 
    $this->firstName = $firstName; 
    $this->lastName = $lastName; 
} 

應該

private $firstName; 
private $lastName; 
public function __construct($firstName, $lastName) 
    { 
     $this->firstName = $firstName; 
     $this->lastName = $lastName; 
    } 

Answer 2

您已經聲明private $firstname和getter中您呼叫$this->firstName資本。