Object-oriented programming (OOP) in PHP for Beginners

Keywords

Definition

I know that many web developers do not like using PHP in their work because of its incoherent syntax and parameters. Conversely, I am a big fan of PHP and like to use it on my website and other works. So that I decided to write a tutorial series about PHP to explain its features which I used mostly; you can find former tutorials on Articles. And, it would be incongruous to not continue with PHP classes and objects.

Class⁽¹⁾

Basic class definitions begin with the keyword class, followed by a class name, followed by a pair of curly braces which enclose the definitions of the properties and methods belonging to the class.

The class name can be any valid label, provided it is not a PHP reserved word. A valid class name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: ^[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*$.

A class may contain its own constants, variables (called "properties"), and functions (called "methods").

The pseudo-variable $this is available when a method is called from within an object context. $this is a reference to the calling object (usually the object to which the method belongs, but possibly another object, if the method is called statically from the context of a secondary object). As of PHP 7.0.0 calling a non-static method statically from an incompatible context results in $this being undefined inside the method. Calling a non-static method statically from an incompatible context has been deprecated as of PHP 5.6.0. As of PHP 7.0.0 calling a non-static method statically has been generally deprecated (even if called from a compatible context). Before PHP 5.6.0 such calls already triggered a strict notice.

Object⁽²⁾

To create a new object, use the new statement to instantiate a class.

Code

Use public to define public variables.

Use the Scope Resolution Operator (also called Paamayim Nekudotayim) to reach static, constant, and overridden properties or methods of a class, well-explained on the code.

Also, you can either write a new function to save each new user to the database or add new features on the createUser function by using MySQLi to improve my tutorial code.


<?php
class user {
  // Define a constant.
  const USER_TYPE = "Premium";
  // Define a private static variable only accessible in the class itself.
  private static $PATH = "Pictures/";
  // Define public variable which can be changed out of the class itself.
  public $firstName;
  public $lastName;
  public $id;
  public $img;
  // Create a function for each new user.
  function createUser($v_1, $v_2, $v_3, $v_4){
   $this->firstName = $v_1;
   $this->lastName = $v_2;
   $this->id = $v_3;
   $this->img = $v_4;
  }
  // Show the former defined user on the database.
  function showUser(){
   echo '<div class="USER">';
   echo '<img src="'.self::$PATH.$this->img.'" />';
   echo '<p>'.$this->firstName.' '.$this->lastName.'<br> { '.$this->id.' }<br><br>';
   echo '<span style="color:red;">'.self::USER_TYPE.'</span></p>';
   echo '</div>';
  }
}

// Create an object named person to get functions and variables from the user class.
$person = new user();
// Create and show a new user.
$person->createUser("Jane", "Doe", "Avengers123", "userDefault.png");
$person->showUser();
?>



Result:

References

⁽¹⁾ http://php.net/manual/en/language.oop5.basic.php

⁽²⁾ http://php.net/manual/en/language.types.object.php