PHP
Creating a post class
Design a Post class that holds title, content and author.
Post class properties
A post carries three core pieces of data: title, content and author. In the Post class you declare three properties for this data: public string $title = "";, public string $content = ""; and public string $author = "";. Each property starts with an empty string default.
Declaring the properties explicitly in the class is good practice: the type string and default "" are clear. Every instance starts in a consistent state and debugging becomes easier.
Setup with __construct
Instead of assigning three properties by hand one by one, you can pass all three values together when creating an instance with the __construct method. You write public function __construct(string $title, string $content, string $author) and inside it add assignments like $this->title = $title;.
So new Post("First post", "Hello world", "Ayşe") gives you a ready post. The $this pseudo-variable points to the instance being created and lets you copy the parameter to the property.
Exercise Add properties and a constructor
Add public string $content = ""; and public string $author = ""; properties to the Post class. Then write a public function __construct(string $title, string $content, string $author) constructor; inside it assign $this->title = $title;, $this->content = $content;, $this->author = $author;. Update the instance to $p = new Post("First post", "Hello world", "Ayşe"); and change the last line to echo $p->title . " - " . $p->author;.
Show example solution
Add public string $content = ""; and public string $author = ""; to the class. Write public function __construct(string $title, string $content, string $author) { $this->title = $title; $this->content = $content; $this->author = $author; }. Create an instance with $p = new Post("First post", "Hello world", "Ayşe"); and print with echo $p->title . " - " . $p->author;.
Example solution:
<?php
// Add properties and a constructor to the Post class
class Post {
public string $title = "";
public string $content = "";
public string $author = "";
public function __construct(string $title, string $content, string $author) {
$this->title = $title;
$this->content = $content;
$this->author = $author;
}
}
$p = new Post("First post", "Hello world", "Ayşe");
echo $p->title . " - " . $p->author;
Test yourself
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Why is the constructor useful?
- To hide the class name
- To pass data once when creating an instance and assign it to properties
- To delete array elements
- To change a variable's type
Show answer
To pass data once when creating an instance and assign it to properties — Correct. The constructor takes data as parameters when an instance is created with new and assigns it to properties, so the instance is ready in one line.
-
Add the parameter list to the constructor
public function __construct(string ____) {
$this->title = $title;
$this->content = $content;
$this->author = $author;
}
Show answer
public function __construct(string $title, string $content, string $author) {
$this->title = $title;
$this->content = $content;
$this->author = $author;
}
-
Match the constructor concepts
- __construct
- Constructor name
- $this->title
- Property assignment
- string $title
- Title parameter
- new Post(...)
- Instantiation
Next lesson: Adding posts with a form
