To define properties in the class, I see two ways:
1
create public variables first, and refer to them inside the __construct() function:
<?php
class User {
public $name;
public $email;
public function __construct($name, $email) {
$this->name = $name;
$this->email = $email;
}
public function getType() {
return $this->type;
}
} ?>
And simply define the properties without defining the public variables:
2
<?php
class Cars{
function __construct($parameter1, $parameter2) {
$this->model= $parameter1;
$this->price = $parameter2;
}
function getPrice(){
echo $this->price ."<br/>";
}
function getModel(){
echo $this->model ." <br/>";
}
} ?>
I'm wondering what is the different usages of these two approaches to define the properties for class in PHP? What's point of using the first option when second option is working the same?
As you said, solution 1 and 2 works but the solution 2 is just a bad way to declare class variables.
By strict convention, always declare your class variables:
You can see the variables of your class in one look. And think about others developers which look after you, it's important to know which variables we can find in this class.
You can define visibility of variables (public, protected, private).
Related
I have been searching for this online, but I can't seem to find something that is clear enough for me to understand. I have seen "similiar" questions on here about this in Java.
class animal{
private $name;
// traditional setters and getters
public function setName($name){
$this->name = $name;
}
public function getName(){
return $this->name;
}
// animal constructors
function __construct(){
// some code here
}
// vs
function __construct($name){
$this->name = $name;
echo $this->name;
}
}
$dog = new animal();
$dog->setName("spot");
echo $dog->getName();
// vs
$dog = new animal("spot");
Should I declare and access my private fields through setters and getters or through the constructor?
Which one is the best practice?
I understand the purpose of a constructor(maybe not), but what is the point of having a constructor if I can declare and access my private fields through setters and getters?
Please note...this is my first time using OOP with web development and PHP, and I'm trying to learn by getting my hands "dirty" by writing some code in order for me to understand certain things in OOP. Please keep it simple.
It is more a matter of semantics than best practice per say.
In your example, your buisness logic may determine that an animal always needs a name.
So it makes sense to construct the object with a name. If you do not want to allow
an animal's name to be changed, then you don't write a setter.
i.e.
class Animal
{
private $name;
public function __construct($name)
{
$this->name = $name;
}
public function getName()
{
return $this->name;
}
}
You may have other properties that an animal doesn't have to have, like an owner
that you only write a getter/setter for i.e.
class Animal
{
private $name;
private $owner;
public function __construct($name)
{
$this->name = $name;
}
public function getName()
{
return $this->name;
}
public function setOwner($owner)
{
$this->owner = $owner
}
}
But if you find that you are always creating an animal with an owner at the same time
you may want to put that in the contructor signature for convenience
class Animal
{
private $name;
private $owner;
public function __construct($name, $owner = null)
{
$this->name = $name;
$this->owner = $owner;
}
public function getName()
{
return $this->name;
}
public function setOwner(Owner $owner)
{
$this->owner = $owner
}
public function getOwner()
{
return $this->owner;
}
}
If the owner is another class in your application, you can type hint that your constructor
needs an owner of a specific type (class). All of this is used to make it easier for you, or another developer to understand some of the requirements/logic behind your code - as well as potentially catching a bug here or there
class Owner
{
private $name;
public function __construct($name)
{
$this->name = $name;
}
}
class Animal
{
private $name;
private $owner;
public function __construct($name, Owner $owner = null)
{
$this->name = $name;
$this->owner = $owner;
}
public function getName()
{
return $this->name;
}
public function setOwner(Owner $owner)
{
$this->owner = $owner
}
public function getOwner()
{
return $this->owner;
}
}
// Create a new owner!
$dave = new Owner('Farmer Dave');
// a standard php empty object
$otherObj = new \stdClass();
// Create a new animal
$daisy = new Animal('Daisy');
// Farmer dave owns Daisy
$daisy->setOwner($dave);
// Throws an error, because this isn't an instance of Owner
$daisy->setOwner($otherObj);
// Set up Maude, with Dave as the owner, a bit less code than before!
$maude = new Animal('Maude', $dave);
Should I declare and access my private fields through setters and getters or through the constructor?
In situations like this, I ask myself:
Why should I create a method just to hold a one line function? (+Constructor)
How painful is it going to be to refactor two, three, four, five or more getters/setters vs one constructor?(+Constructor)
How hard is it going to be to document two, three, four, five or more getters/setters vs one constructor?(+Constructor)
Is there going to be a default value which will be documented? (+Constructor)
Do I like documentation and expect people to read? (+Constructor)
Will the initial value be undefined?(+Setter)
Is there a set of equivalent forms (shorthand, international, nicknames) which will all be acceptable as syntatically correct for required arguments? (+Setter)
Is there a set of optional arguments with default values? (+Setter)
Is there a common need to stringify and parse the initial value? (+Setter)
Do I dislike documentation and expect people to experiment? (+Setter)
Which one is the best practice?
The Date object seems to be the most complex class in most languages, so its PHP implementation would be a good reference for best practices.
What is the point of having a constructor if I can declare and access my private fields through setters and getters?
A constructor is implicitly invoked upon object instantiation in order to encapsulate the default state of the resulting data structure of its type.
References
DateTime::__construct
date_create
The DateTime class
date_default_timezone_get
date_default_timezone_set
Changes in PHP datetime support
PHP OOP: Accessor and Destructor Methods
Concurrency, part 4: Comparing promises frameworks in different languages – SLaks.Blog
CDD: Context-Driven Development
Depends. Usually one say: If it's a required dependency, use the constructor, if it's optional, use getter/setter.
There is no preference for, or against one of them.
The constructor contains code, that is executed right after the object is created and it should leave the object in a stable and useable state. Thats the idea behind the constructor and it doesn't work in any case, but it should give you an idea, what should go into it.
Note, that you can even implement both constructor arguments and setters for the same property, for example if you want to allow to replace property later.
$bingo = new Dog;
echo $bingo->getName(); // DogHasNoNameException <-- maybe better as constructor argument?
$bingo = new Dog('Bingo');
echo $bingo->getName(); // "Bingo"
$spike = new Dog; // Missing argument
$bingo->setName('Spike'); // Or maybe "rename()" ;)
echo bingo->getName(); // "Spike"
Should I declare and access my private fields through setters and
getters or through the constructor? Which one is the best practice?
Both. It depends on your needs. If need a value in certain fields you add a param to the
__construct()-Method to do so. Or you can also add an optional Param to __construct to give the user the option to set the attribute
I understand the purpose of a constructor(maybe not), but what is the
point of having a constructor if I can declare and access my private
fields through setters and getters?
The contructor should initialize your attributes which need to be initialized.
In my opinion, it is more correct to write setter's & getter's, since then, the number of properties will only grow. And the __construct can then take an array of properties of the names of the keys (property => value), and set them to properties.
1 > That's your chose : if dependency is required, good practise use the constructor, else, use getter.
2 > for the best practise is the first,
Actually, you have a name, for your animal, but if you add a type and sex? and you want to call type, sexe or name separatly, first method is more better than the second.
class animal{
private $name, $type, $sex;
// traditional setters and getters
public function setName($name){
$this->name = $name;
}
public function setSex($sex){
$this->sex = $sex;
}
public function setType($type){
$this->type = $type;
}
public function getName(){
return $this->name;
}
public function getSex(){
return $this->sex;
}
public function getType(){
return $this->type;
}
// animal constructors
function __construct(){
// some code here
}
}
$dog = new animal();
$dog->setName("spot");
$dog->setSexe("male");
$dog->setType("dog");
echo $dog->getName().' is a '.$dog->getType().'('.dog->getSex().')';
3 > that depends first question... BUt Globaly we are always one dependency required, for sample:
class animal{
private $name, $type, $sex;
// traditional setters and getters
public function setName($name){
$this->name = $name;
}
public function setSex($sex){
$this->sex = $sex;
}
private function setType($type){
// if type is string ( cat, dog, lion ) and you want
// to linked string in an id in your database (1, 2, 3...).
// you want to call your database connection ( declared in you constructor)
// and search type id here.
$this->type = $type;
}
public function getName(){
return $this->name;
}
public function getSex(){
return $this->sex;
}
public function getType(){
return $this->type;
}
// animal constructors
public function __construct($type){
// for sample you want to open your database here
this->setType($type);
}
public function __destruct(){
// and you want to close your connection here.
}
}
I have $name and $age defined in set_name() and set_age.
Please check index.php:
<?php
// This part needs some fixing.
class Pet {
public $name;
public $age;
// get() and set() functions for name
function set_name($name) {
$this->name = $name;
}
function get_name() {
return $this->$name;
}
// get() and set() functions for age
function set_age($age) {
$this->age = $age;
}
function get_age() {
return $this->$name;
}
}
.....
Edit:
This problem is fixed. No need for new answers!
You need constructor for your classes and don't do the makeSound method in your Pet class static. Try this:
public Cat(){
makeSound(sound);
}
public Dog(){
makeSound(sound);
}
Your method declaration is wrong. If a parent has an implemented version of a function, you do not need to declare it in the subclass. But even if you would want to, the correct way to do it (thus overriding the parent function) would be:
void makeSound(String sound) {
System.out.println("Hi, I make a " + sound);
}
The use of a static keyword would not make much sense. A static method is a method that is part of the class and not of the created objects. Meaning you could call the method like this Pets.makeSound(...)
I am trying to extend static class in PHP. What I am running into is that once I change the variable in one of the extend classes, all others classes are changes as well. This is what I am trying to do:
class Fruit{
private static $name = Null;
public static function setName($name){
self::$name = $name;
}
public static function getName(){
return self::$name;
}
}
class Apple extends Fruit{};
class Banana extends Fruit{};
Apple::setName("apple");
Banana::setName("Banana");
echo Apple::getName();
echo Banana::getName();
I have read about late static binding and the keyword static::. But I cannot think of a way how to accomplish this without having to redeclare all Fruit's methods in both Apple and Banana.
I will be happy for any help
Thank You
This works:
<?php
class Fruit{
protected static $name = Null;
public static function setName($name){
static::$name = $name;
}
public static function getName(){
return static::$name;
}
}
class Apple extends Fruit{protected static $name;};
class Banana extends Fruit{protected static $name;};
Apple::setName("apple");
Banana::setName("Banana");
echo Apple::getName();
echo Banana::getName();
Unfortunately you need to re-declare the static properties you want to specialize, but your late static binding intuition was right :)
Although you should avoid such constructions, you could solve it quite nicely:
<?php
class Fruit {
protected static $names;
public static function setName($name)
{
self::$names[get_called_class()] = $name;
}
public static function getName()
{
return isset(self::$names[$key = get_called_class()]) ? self::$names[$key] : null;
}
}
So basically you store the data in just a single class, but specific to the class the method was called on. You don't need static as $name is always part of self, but 5.3 is still required because get_called_class is also part of late static binding.
quick question:
Is it considered bad practice to set something in a Construct function like so:
Class whatever {
$var = "";
public function __construct($var){
$this->var = $var;
}
//And then return it in another function like
public function getVar(){
return $this->var;
}
}
Yes, it is bad practice since you not declare $var and not are using a setter method. The meaning with getter and setter methods completely vanyshes when you not declare the variable, and not declare it private or protected. Then you could just go with $class->var=something.
Class whatever {
private $var;
public function __construct($var){
$this->setVar($var);
}
public function setVar($var){
$this->var = $var;
}
public function getVar(){
return $this->var;
}
}
no it is a good practice .
suppose you have 20 fields , and you must fill them to use class correctly .
good practice is to initialize them in the construction . if you use setter you must call 20 methods .
You have good answers, but I'll give you a rundown on some more info
what is the constructor for?
Use a constructor in your classes if your class instances need initialization
a getter for variables set in the constructor could be useful as a way to find out how the instance was initialized
setters
You need these when you need to modify the behaviour of your instance, or when you want to load data into it
getters
The only way to retrieve the contents of the instance (public properties are not encouraged due to a plethora of reasons)
My example
Feel free to do what you wish with this, it's only an example and it's obviously not doing anything. If you want to ask anything about this, please do
<?php
class AnExampleClass {
// this is convenient sometimes but I don't recommend it
public $public = '';
protected $protected;
private $private;
public function __construct($private, $protected){
$this->private = $private;
$this->setProtected($protected);
}
public function getPrivate(){
return $this->private;
}
public function getProtected() {
return $this->protected;
}
public function setProtected($protected) {
// only allow boolean
$this->protected = (bool)$protected;
}
public function __get($name) {
// read the manual on this magic
}
public function __set($name, $value) {
// read the manual on this magic
}
}
Just wondering if you could shed some light on best practices?
Would having a load method in a Class be the correct/best way?
Class Test extends Foo{
public $id;
public $name;
public function __construct()
{
parent::__construct();
}
public function load($id, $name)
{
$this->id = $id;
$this->name = $name;
}
}
Or would it be concidered better practice to just have the load method logic in the constructor?
Class Test extends Foo{
public $id;
public $name;
public function __construct($id, $name)
{
parent::__construct();
$this->id = $id;
$this->name = $name;
}
}
The 2nd option seems to be more logical to me as it's one less method and it's called automatically etc, however, I've seen the 1st option more often. Is there a reason for this? Any help would be appreciated!
The second option is best. A constructor is meant to prepare the object for use. It is the perfect place to initialize properties etc. Unless you have a good reason for using load() instead of the constructor, go with the second example.
The first option uses slightly more abstraction, I suppose.
I can see a situation where you might need to copy the code and separating the variable assignments into a load() or init() function might make your code a litter easier to update for the new purpose.
An advantage of the 1st option is that you don't require the developer to supply the information straight away. Although it is more error prone since one might forget about calling the load function. If all other functions require $id and $name to be set it's best to require the arguments when creating a new object.
On the other hand not having the load function prevents you from reloading the object with new values later on in the code.
You can combine the two by calling the load function from the constructor:
Class Test extends Foo{
public $id;
public $name;
public function __construct( $id, $name )
{
parent::__construct();
$this->load( $id, $name );
}
public function load($id, $name)
{
$this->id = $id;
$this->name = $name;
}
}
OR if you don't require the values to be set on creation you can use PHPs funky function overloading stuff:
Class Test extends Foo{
public $id;
public $name;
public function __construct()
{
parent::__construct();
if( func_num_args() === 2 ){
call_user_func_array(array($this, 'load'), func_get_args() );
}
}
public function load($id, $name)
{
$this->id = $id;
$this->name = $name;
}
}
You could extend load() per particular member.
Making each property protected or private and providing a set/get function for one of them.
That's an acceptable way and sometimes is better than overloading your constructor with dependencies and logic.
Try this and see if it helps you:
Class Test extends Foo{
protected $id;
protected $name;
public function __construct()
{
parent::__construct();
}
public function setId($id) {
$this->id = $id;
}
public function setName($name) {
$this->name = $name;
}
public function getId() {
return $this->id;
}
public function getName() {
return $this->name;
}
}
It's called getters and setters and it's a more clean and robust approach.
Besides, as mentioned in other answers - It provides better re-usability, ability to have your object clean of data with null values, but that's all dependent on what is the intent of your class!