What is the difference between class and function in php? [closed] - php

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I have used the following codes my self, both of them gave the same result. Then why we are using class instead of a normal function, and what is the difference between classes and functions.
<?php
class MyClass{
public $property = "This is My Class Property";
public function getProperty(){
echo $this->property."<br />";
}
}
$obj=new MyClass();
echo $obj->getProperty();
?>
<?php
function getProp(){
$prop="This is My Class Property";
echo $prop;
}
getProp();
?>

Answer 1

The PHP Language reference has details on what a function and class is:
http://www.php.net/manual/en/langref.php
It also explains most the other features of PHP. If want to learn PHP that is the best place to start.
Functions
The function is a grouping of statements (lines of code).
For example the following statements:
$name = 'mary';
$gender = 'girl';
if ($gender == 'girl') {
$line = $name . ' had a little pony.';
} else if ($gender == 'boy') {
$line = $name . ' had a little horse.';
}
echo $line;
Can be grouped together into a function so it can be reused:
getSentence('mary', 'girl');
getSentence('peter', 'boy');
function getSentence($name, $gender) {
if ($gender == 'girl') {
$line = $name . ' had a little pony.';
} else if ($gender == 'boy') {
$line = $name . ' had a little horse.';
}
echo $line;
}
Notice the two function calls:
getSentence('mary', 'girl');
getSentence('peter', 'boy');
These two statements run the whole block of code inside the getSentence function and pass it the variables $name and $gender.
With the first function $name = 'mary' and $gender = 'girl' and in the second $name = 'peter' and $gender = 'boy'.
So the main benefit of functions is that you have grouped code for reuse, allowing the passing of different values for the variables needed by the function. These variables are called the function parameters.
Another benefit of having the code grouped is easier readability. You are essentially naming the block of code, and giving them a specific purpose. Making it easy to read and remember it's use.
Another benefit is that redundancy is removed. You do not have to write the block of code more then once. You just define it once, and call it multiple times. This also makes editing of the function code affect all calls to that function - which reduces errors in having to edit multiple locations when changing just one aspect.
eg:
We can make sure the $name string has an uppercase first character.
function getSentence($name, $gender) {
$name = ucfirst($name);
if ($gender == 'girl') {
$line = $name . ' had a little pony.';
} else if ($gender == 'boy') {
$line = $name . ' had a little horse.';
}
echo $line;
}
We made just one change, and it affected every function call to getSentence(). In this case both:
getSentence('mary', 'girl');
and
getSentence('peter', 'boy');
Classes are a grouping of functions.
class Play {
function getSentence($name, $gender) {
$name = ucfirst($name);
if ($gender == 'girl') {
$line = $name . ' had a little pony.';
} else if ($gender == 'boy') {
$line = $name . ' had a little horse.';
}
echo $line;
}
function getSong($name) {
// code here
}
}
All we did was put
class Play { /** functions here **/ }
around a group of functions.
This offers the same benefits that functions do for statements except classes does it for functions.
Classes go further to build a programming methodology called Object Oriented programming (OOP), which you can read more about in link to PHP Language reference.
This defines classes as the template or definition of Objects. Objects being similar to real world objects, with the functions being called "methods" that can be called for the object.
So the class Play can be thought of as the object called "Play" with the methods "getSentence" and "getSong". These methods can then manipulate the properties of the object "Play" or return useful information about "Play". In this way, all the code inside Play becomes independent of code elsewhere in the program.
When the code inside Play requires some code elsewhere to function, it can be brought in using "inheritance", which is a major part of OOP. I will not go into detail about this as it is a very broad topic.
I would recommend getting a book on OOP and reading it to really understand why you should use classes and methods and when to use them.

Answer 2

Any function can be invoked as a constructor with the keyword new and the prototype property of that function is used for the object to inherit methods from.
functions are set of instructions or procedures for doing a certain task. for example, shooting a gun has a set of procedures to perform. raising your gun, taking aim, etc.
however, these procedures are dependent on each other. that is raising a gun means nothing alone.
in classes however you can create objects.
in objects , you can create for example, a gun. this gun has different functions associated with it like raising the gun, taking aim.
in effect the object can exist in its own and can be reused for later purposes.
class SimpleClass
{
// property declaration
public $var = 'a default value';
// method declaration
public function displayVar() {
echo $this->var;
}
}
so when you want to use the class object you need to declare
$objectSimple = new SimpleClass();
and when you want to use the class method than you need to declare
$objectSimple->displayVar();
as in your example
<?php
class MyClass{
public $property = "This is My Class Property";
public function getProperty(){
echo $this->property."<br />";
}
}
$obj=new MyClass();
echo $obj->getProperty();
?>
<?php
function getProp(){
$prop="This is My Class Property";
echo $prop;
}
getProp();
?>
yes you both will work. after reviewing your sample seems like you are asking for OOP vs procedural.
They don't really have pros and cons at all, IMO. They're simply different approaches to the same problems.
In a purely procedural style, data tends to be highly decoupled from the functions that operate on it.
In an object oriented style, data tends to carry with it a collection of functions.
In a functional style, data and functions tend toward having more in common with each other (as in Lisp and Scheme) while offering more flexibility in terms of how functions are actually used. Algorithms tend also to be defined in terms of recursion and composition rather than loops and iteration.
Of course, the language itself only influences which style is preferred.

Answer 3

You could say that a class is just a group of functions, but really it's so much more than that.
Think of a class as a group of functions that are used to manipulate the same amount of data.
Say you pull a user from the database. You would have to assign many variables accross multiple pages if you had any sort of complexity to your member system.
An easier way would be..
$user = new user(2)[/php) (assuming user is the class, and 2 is the userid it pulls from the databse, your contructor function would populate all of the users information, which is easily grouped together and used like...
[code=php:0]print "Hello ". $user->firstName . " welcome to thiswebsite. Your last login was " . $user->lastLogin
It's really a small and silly example, but if you let yourself think a little at the possibilities (and this isnt the only one, polymorphism is another GREAT feature of classes)

Answer 4

Usually when you use a function you intend to get information from it once, and then the function will forget the data it sent you (unless you're creating a site variable, or constant in it...)
A class you might want to create if you want to continue to use information. For example, a customer signs in, and wants to look through six different pages about their account. You'd probably want to create a class so that immediately when the customer signs in, you have information on that customer, that you don't have to continually make sql calls to get.
Maybe at the top of the screen you wish to put their status, and their billing info. You would get this information when they log in, and put in the constructor. Then no matter what page they go to, this information will be quickly available.