apt-get install mysql-server mysql-client
apt-get install apache2
apt-get install php5 libapache2-mod-php5
apt-cache search php5
apt-get install php5-mysql php5-curl php5-gd php5-intl php-pear php5-imagick php5-imap php5-mcrypt php5-memcache php5-ming php5-ps php5-pspell php5-recode php5-snmp php5-sqlite p$
apt-get install phpmyadmin
/etc/init.d/apache2 restart
service 11.html (local)
<!DOCTYPE html>
<html>
<head>
<style>
h1 {
border-bottom: 3px solid #cc9900;
color: #996600;
font-size: 30px;
}
table, th , td {
border: 1px solid grey;
border-collapse: collapse;
padding: 5px;
}
table tr:nth-child(odd) {
background-color: #f1f1f1;
}
table tr:nth-child(even) {
background-color: #ffffff;
}
</style>
</head>
<body>
<h1>Nama Sekolah</h1>
<div id="id01"></div>
<script>
var xmlhttp = new XMLHttpRequest();
var url = "http://ambo-kena.besaba.com/mreport/namasekolah.php";
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
myFunction(xmlhttp.responseText);
}
}
xmlhttp.open("GET", url, true);
xmlhttp.send();
function myFunction(response) {
var arr = JSON.parse(response);
var i;
var out = "<table>";
for(i = 0; i < arr.length; i++) {
out += "<tr><td>" +
arr[i].Id +
"</td><td>" +
arr[i].Title +
"</td><td>" +
arr[i].Content +
"</td></tr>";
}
out += "</table>"
document.getElementById("id01").innerHTML = out;
}
</script>
</body>
</html>
namasekolah.php
<?php
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");
$conn = new mysqli("mysql.hostinger.my", "contoh_username_bro", "password_bro", "contoh_nama_database");
$result = $conn->query("SELECT post_id,post_title, post_content FROM posts");
$outp = "[";
while($rs = $result->fetch_array(MYSQLI_ASSOC)) {
if ($outp != "[") {$outp .= ",";}
$outp .= '{"Id":"' . $rs["post_id"] . '",';
$outp .= '"Title":"' . $rs["post_title"] . '",';
$outp .= '"Content":"'. $rs["post_content"] . '"}';
}
$outp .="]";
$conn->close();
echo($outp);
?>
Contoh printscreen:
SQL:
-- phpMyAdmin SQL Dump
-- version 3.5.2.2
-- http://www.phpmyadmin.net
--
-- Host: localhost
-- Generation Time: Jan 07, 2015 at 05:35 AM
-- Server version: 5.1.67
-- PHP Version: 5.2.17
SET SQL_MODE="NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";
/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;
--
-- Database: `u641767033_mrpt`
--
-- --------------------------------------------------------
--
-- Table structure for table `posts`
--
CREATE TABLE IF NOT EXISTS `posts` (
`post_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`post_title` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
`post_content` text COLLATE utf8_unicode_ci NOT NULL,
`post_date` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (`post_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=90 ;
--
-- Dumping data for table `posts`
--
INSERT INTO `posts` (`post_id`, `post_title`, `post_content`, `post_date`) VALUES
(1, 'MAAHAD MUHAMMADI (LELAKI)', '09-744 4003', '0000-00-00 00:00:00'),
(2, 'MAAHAD MUHAMMADI (PEREMPUAN)', '09-748 2549', '0000-00-00 00:00:00'),
(3, 'MAAHAD PENGAJIAN ISLAM', '09-748 3804', '0000-00-00 00:00:00');
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
OOP was first invented for the purpose of physical modelling in the Simula-67.
Whilst there is no hard and fast definition of what Object Oriented Programming (OOP) is, we can define. So lets just use this loose definition for now and it is left to reader to make up their own minds about what a decent definition is. Object Oriented Programming (OOP) is a programming concept that treats functions and data as objects. OK, not the best definition but gives us an opening. The key word here is objects. As we progress through this tutorial we will see how data and functions can be represented as re-usable objects, thus cutting down on code and time.
Simply put, an oject is a bunch of variables and functions all lumped into a single entity. The object can then be called rather than calling the variables or functions themselves. Within an object there are methods and properties. The methods are functions that manipulate data withing the object. The properties are variables that hold information about the object.
A class is the blueprint for your object. The class contains the methods and properties, or the charactaristics of the object. It defines the object. Lets just start with some examples to see how it all pieces together. We will use a vehicle as our object. All vehicles share similar charactaristics, eg: number of doors, they are painted some color, they each have a price. All vehicles do similar things also, drive, turn left, turn right, stop etc. These can be described as functions, or in OOP parlance, methods. So, the class holds the definition, and the object holds the value. You declare class in PHP by using the class keyword.
<?php
class vehicle{
/*** define public properties ***/
/*** the color of the vehicle ***/
public $color;
/*** the number of doors ***/
public $num_doors;
/*** the price of the vehicle ***/
public $price;
/*** the shape of the vehicle ***/
public $shape;
/*** the brand of vehicle ***/
public $brand;
/*** the constructor ***/
public function __construct(){
echo 'About this Vehicle.<br />';
}
/*** define some public methods ***/
/*** a method to show the vehicle price ***/
public function showPrice(){
echo 'This vehicle costs '.$this->price.'.<br />';
}
/*** a method to show the number of doors ***/
public function numDoors(){
echo 'This vehicle has '.$this->num_doors.' doors.<br />';
}
/*** method to drive the vehicle ***/
public function drive(){
echo 'VRRROOOOOOM!!!';
}
} /*** end of class ***/
?>
With this simple class definition we can now create one, or many, vehicle objects. Lets see how its done, then we will step through it all. To create a new object from the class definition we use the new keyword.
<?php
/*** create a new vehicle object ***/
$vehicle = new vehicle;
/*** the brand of vehicle ***/
$vehicle->brand = 'Porsche';
/*** the shape of vehicle ***/
$vehicle->shape = 'Coupe';
/*** the color of the vehicle ***/
$vehicle->color = 'Red';
/*** number of doors ***/
$vehicle->num_doors = 2;
/*** cost of the vehicle ***/
$vehicle->price = 100000;
/*** call the showPrice method ***/
$vehicle->showPrice();
/*** call the numDoors method ***/
$vehicle->numDoors();
/*** drive the vehicle ***/
$vehicle->drive();
?>
Using the combination of the two code boxes above, you should have something like..
About this vehicle.
This vehicle costs 100000.
This vehicle has 2 doors.
Lets step through the class definition first to see what its all about.
We began the class with the class keyword. This tells PHP that what follows is a class definition.
<?php
class vehicle{
?>
Next we declared some variables, or as they are known in the OOP world, properties.
<?php
/*** the color of the vehicle ***/
public $color;
/*** the number of doors ***/
public $num_doors;
/*** the price of the vehicle ***/
public $price;
/*** the shape of the vehicle ***/
public $shape;
/*** the brand of vehicle ***/
public $brand;
?>
<?php
/*** the constructor ***/
public function __construct(){
echo 'About this vehicle.<br />';
}
?>
The constructor method (function) is a special function that is executed every time a new object is created or "instantiated". If a class needs to do something before running some code, then this is the place to do it. It is often used to set properties within the class. You may pass a variable directly to the constructor from your code, but more of that later. Following the constructor is several methods (functions) that do things. These methods are also preceded by the public meaning they are available with the scope of your code.
<?php
/*** a method to show the vehicle price ***/
public function showPrice(){
echo 'This vehicle costs '.$this->price.'.<br />';
}
/*** a method to show the number of doors ***/
public function numDoors(){
echo 'This vehicle has '.$this->num_doors.' doors.<br />';
}
/*** method to drive the vehicle ***/
public function drive(){
echo 'VRRROOOOOOM';
}
?>
As you see above, our methods are similar to normal PHP functions. However you may note the use of variables like $this->price and $this->num_doors. The keyword $this is used to refer to properties or methods within the class itself. The $this keyword is reserved in PHP, so it cannot be used as a variable or property name. Finally we finished our class definition with a closing }. I like to put a comment beside it so I dont delete it or get it confused with a function I am writing.
Following on from the class definition we see our userland code. This is the code we use to instantiate (create) a new instance, or new object, of our vehicle class. As mentioned earlier we do this with the use of the new keyword.
<?php
/*** create a new vehicle object ***/
$vehicle = new vehicle;
?>
The code above creates a new object from our class definition called $vehicle. It is at this time that the constructor is called and any code within the constructor is executed. Once we have a new object we can then begin to assign values to the properties of that object as seen here.
<?php
/*** the brand of vehicle ***/
$vehicle->brand = 'Porsche';
/*** the shape of vehicle ***/
$vehicle->shape = 'Coupe';
/*** the color of the vehicle ***/
$vehicle->color = 'Red';
/*** number of doors ***/
$vehicle->num_doors = 2;
?>
With the properties set as above, it is now simple to use the object methods to manipulate the object by calling the methods. The methods are executed like this below.
<?php
/*** call the showPrice method ***/
$vehicle->showPrice();
/*** call the numDoors method ***/
$vehicle->numDoors();
/*** drive the vehicle ***/
$vehicle->drive();
?>
So, thats the step-by-step of your first class. You see how easy it would be now to create a new car object. Perhaps a Red Ferrari with 4 doors costing $250,000.00.
In the previous sections you have seen comments for almost every line of code. This is a good practice, although some may find it excessive, as it may not be you who has to edit the code next time. OOP can get very abstracted and if you are not careful it is easy to lose site of your programmatical work flow. Most methods within a class will return a value, rather than echo a line of HTML code. A class method may also take one, or several, arguements. It is good practice to show what these arguements are and there types. An example follows below.
<?php
/**
* adds an array of numbers and returns the value
*
* @param array $numbers An array of numbers to add
*
* @access private
*
* @return int Returns sum of numbers
*
*/
private function sum_of_numbers($numbers){
/*** return the sum of the $numbers array ***/
return array_sum($numbers);
}
?>
The above function is rather simplistic, but shows well the commenting of code. The comments begin in a block of C type multiline comments and gives us a brief description of what it does, followed by the parameter it takes, in this case an array of numbers. It tells us that access to the function is private (more on this in the next section). Finally the comment block tells us that the return value is of type INT. We can also see within the function itself a single line comment just to show what is happening within the funtion itself. If you follow these practices you code will always be readable and easy to follow by yourself and others.
Probably the greatest feature of the PHP OOP model is Inheritence. Inheritence is the ability of php to extend classes (child classes) that inherit the charactaristics of the parent class. The resulting object of an extend class has all the charactaristics of the parent class, plus whatever is in the new child, or extended class. In this instance we will extend the vehicle class and add a motorcyle. A motorcycle is still a vehicle and shares many of the same attributes such as price, drive etc. But a motorcycle has some unique features that a car does not.
Rather than type out the whole of the vehicle class definition again, we will save it in a file of its own called vehicle.class.php. It is important here to note the naming convention here as it will be important later in this tutorial. Lets see how it works.
<?php
/*** include the vehicle class definition ***/
include('vehicle.class.php');
class motorcycle extends vehicle{
/*** the number of side cars ***/
private $num_sidecars;
private $handlebars;
/**
*
* set the type of handlebars
*
* @access public
*
* @param string
*
* @return string
*
**/
public function setHandlebars($handlebarType){
$this->handlebars=$handlebarType;
}
/**
*
* Set number of side cars
*
* @access public
*
* @param int
*
* @return int
*
**/
public function setSidecar($numSidecars){
$this->numSidecars = $numSidecars;
}
/**
*
* Show the numbers of sidecars
*
* @return string
*
**/
public function showSideCar(){
echo 'This motorcyle has '. $this->numSidecars.' sidecar<br />';
}
} /*** end of class ***/
/*** our userland code ***/
/*** create a new vehicle object ***/
$vehicle = new motorcycle;
/*** the brand of vehicle ***/
$vehicle->brand = 'Harley Davidson';
/*** the shape of vehicle ***/
$vehicle->shape = 'Sportster';
/*** the color of the vehicle ***/
$vehicle->color = 'Black';
/*** number of doors ***/
$vehicle->num_doors = 0;
/*** cost of the vehicle ***/
$vehicle->price = 25000;
/*** type of handle bars ***/
$vehicle->setHandlebars('Ape Hangers');
/*** set the sidecar ***/
$vehicle->setSidecar(1);
/*** show the vehicle brand and type ***/
echo $vehicle->brand.': '.$vehicle->shape.'<br />';
/*** call the showPrice method ***/
$vehicle->showPrice();
/*** show the sidecars ***/
$vehicle->showSideCar();
/*** drive the vehicle ***/
$vehicle->drive();
?>
If you run the above code with out including the parent class, you will get a Fatal Error like this:
Fatal error: Class 'vehicle' not found in /www/oop.php on line 3
This means when you use an object or wish to extend from it. you must include the class file. Either as code, or most commonly, with an include() statement.
The visibility of class members, (properties, methods), relates to how that member may be manipulated within, or from outside the class. Three levels of visibilty exist for class members.
By default, all class members are public. This means if you do not declare a property or method within the class, it will be public. It is good practice to declare the visibility of class members for the sake of readability for yourself and others. It is much easier for another programmer to see your intentions. This will also future proof your scripts should access modifiers be deprecated.
Public class members (properties and methods) are available through-out the script and may be accessed from outside the class as we demonstrated in our car class. Lets create a simple new class to demonstrate.
<?php
class mathematics{
/*** a number ***/
public $num;
/**
*
* Add two to a number
*
* @access public
*
* @return int
*
**/
public function addTwo(){
return $this->num+2;
}
}/*** end of class ***/
/*** Instantiate a new class instance ***/
$math = new mathematics;
/*** set the value of the number ***/
$math->num = 2;
/*** call the addTwo method ***/
echo $math->addTwo();
?>
We can see in the above example that the public variable $num is set from user space and we call a public method that adds two the number and returns the value of $num+2. Having our properties (variables) visible, or accessible from any part of our script works in our favour here, but it can also work against us. A could arise if we lost track of our values and changed the value of $num. To counter this problem we can create a method to set the value for us. Even with this in place it is still possible for somebody to simply access the $num variable. So we make the variable private. This ensures us that the property is only available within the class itself. It is private to the calling class. Consider the following code.
<?php
class mathematics{
/*** a number ***/
private $num;
/**
*
* Set the value of $num
*
* @access public
*
* @param $num The number to set
*
* @return int
*
**/
public function setNum($num){
$this->num = $num;
}
/**
*
* Add two to a number
*
* @access public
*
* @return int
*
**/
public function addTwo(){
return $this->num+2;
}
}/*** end of class ***/
/*** Instantiate a new class instance ***/
$math = new mathematics;
/*** set the value of the number ***/
$math->setNum(2);
/*** call the addTwo method ***/
echo $math->addTwo();
?>
?>
Any further attempt to reset the $num property without the setNum() method would result in a Fatal Error such as
Fatal error: Cannot access private property mathematics::$num in /www/mathematics.class.php on line 43
Even if you were to try to access the private $num property from a child class it would fail. This is because private methods and properties in a parent class are not visible to child classes and cannot be accessed. To access a parent method or property from a child class you need to use the protected keyword. Like the private keyword, protetected methods and properties are available only to the class that created them. But unlike private, protected methods and properties are visible from a parent class. Lets see how this works.
<?php
class mathematics{
/*** a number ***/
protected $num;
/**
*
* Set the value of $num
*
* @access public
*
* @param $num The number to set
*
* @return int
*
**/
public function setNum($num){
$this->num = $num;
}
/**
*
* Add two to a number
*
* @access public
*
* @return int
*
**/
public function addTwo(){
return $this->num+2;
}
}/*** end of class ***/
class divide extends mathematics{
/**
*
* Divide a number by two
*
* @access public
*
* @return int
*
**/
public function divideByTwo(){
/*** divide number by two ***/
$new_num = $this->num/2;
/*** return the new number and round to 2 decimal places ***/
return round($new_num, 2);
}
} /*** end of class ***/
/*** Instantiate a new class instance ***/
$math = new divide;
/*** set the value of the number ***/
$math->setNum(14);
echo $math->divideByTwo();
?>
We can see here the the user space code has called the setNum() method in the parent mathematics class. This method, in turn, sets the $num property. We are able to do this because the $num property has been declared protected and is visible to the child class.
As we saw in the previous section there are ways to protect your code from being used in an improper manner. Another way of protecting yourself is the Final keyword. Any method or class that is declared as Final cannot be overridden or inherited by another class. Lets put it to the test.
<?php
final class mathematics{
} /*** end of class ***/
class divide extends mathematics{
}
?>
By running the above code you will get an error such as
Fatal error: Class divide may not inherit from final class (mathematics) in /www/final.php on line 8
This can protect us from those who wish to use our code for a purpose other than that for which it was intended.
An abstract class is a class that cannot be instantiated on its own. You cannot create a new object from it. To see this lets make a basic class.
<?php
abstract class mathematics{
/**
*
* Add two to a number
*
* @access public
*
* @return int
*
**/
public function addTwo(){
return $this->num+2;
}
} /*** end of class ***/
/*** try to create new object from the mathematics class ***/
$math = new mathematics
?>
Using the code above, you will get an error something like this
Fatal error: Cannot instantiate abstract class mathematics in /www/abstract.php on line 23.
As you can see, this is not allowed. Also if you declare any class method to be abstract, you must also declare the class itself as abstract too. So, whats the point you ask? Well, you can inherit from an abstract class. Any class that extends an abstract parent class must create an interface of the parent abstract methods. If this is not done a fatal error is generated. This ensures that the implementation is correct.
<?php
abstract class mathematics{
/*** child class must define these methods ***/
abstract protected function getMessage();
abstract protected function addTwo($num1);
/**
*
* method common to both classes
*
**/
public function showMessage() {
echo $this->getMessage();
}
} /*** end of class ***/
class myMath extends mathematics{
/**
*
* Prefix to the answer
*
* @return string
*
**/
protected function getMessage(){
return "The anwser is: ";
}
/**
*
* add two to a number
*
* @access public
*
* @param $num1 A number to be added to
*
* @return int
*
**/
public function addTwo($num1) {
return $num1+2;
}
} /*** end of class ***/
/*** a new instance of myMath ***/
$myMath = new myMath;
/*** show the message ***/
$myMath->showMessage();
/*** do the math ***/
echo $myMath->addTwo(4);
?>
The use of the static keyword allows class members (methods and properties) to be used without needing to instantiate a new instance of the class. The static declaratin must come after the visibility declaration, eg:
public static myClass{
Because there is no object created when using a static call, the keyword $this and the arrow operator, -> are not available. Static variables belong to the class itself and not to any object of that class. To access withing the class itself you need to use the self keyword along with the :: scope resolution operator. Lets whip up a quick example of using static.
<?php
/*** a simple class ***/
class myClass{
/*** a static variable ***/
static $foo;
}
/** give the static variable a value ***/
myClass::$foo = 'Bar';
/*** echo the static variable ***/
echo (myClass::$foo ).
?>
The above snippet will echo
Bar
This is rather basic as an example, so lets use something practical. Static properties are often used as counters. Here we will use a basic counter class.
<?php
class counter{
/*** our count variable ***/
private static $count = 0;
/**
* Constructor, duh
**/
function __construct() {
self::$count++;
}
/**
*
* get the current count
*
* @access public
*
* @return int
*
**/
public static function getCount() {
return self::$count;
}
} /*** end of class ***/
/*** create a new instance ***/
$count = new counter();
/*** get the count ***/
echo counter::getCount() . '<br />';
/*** create another instance ***/
$next = new counter();
/*** echo the new count ***/
echo counter::getCount().'<br />';
/*** and a third instance ***/
$third = new counter;
echo counter::getCount().'<br />';
?>
Hopefully by the end of the above snippet you can see what is happening. At each new instance the counter class we increment by one. Not also the use of the :: scope resolution operator and self keyword to refer to the static variable within the class itself.
Interfaces in PHP allow you to define a common structure for your classes. An interface cannot be instantiated on its own. One of the goals of OOP is re-use of code. Interfaces make this a much easier process. The interface methods have no internal logic, they are simply a "mapping" or constraint of what the class, or classes, should implement. Here we will demonstrate how this works using our vehicle class from earlier, with the addition of a stop() function.
<?php
class vehicle implements testdrive{
/*** define public properties ***/
/*** the color of the vehicle ***/
public $color;
/*** the number of doors ***/
public $num_doors;
/*** the price of the vehicle ***/
public $price;
/*** the shape of the vehicle ***/
public $shape;
/*** the brand of vehicle ***/
public $brand;
/*** the constructor ***/
public function __construct(){
echo 'About this Vehicle.<br />';
}
/*** define some public methods ***/
/*** a method to show the vehicle price ***/
public function showPrice(){
echo 'This vehicle costs '.$this->price.'.<br />';
}
/*** a method to show the number of doors ***/
public function numDoors(){
echo 'This vehicle has '.$this->num_doors.' doors.<br />';
}
/*** method to drive the vehicle ***/
public function drive(){
echo 'VRRROOOOOOM!!!';
}
/**
* a method to stop the car
*
* @access public
*
**/
public function stop(){
echo 'SSSCCRRREEEEEECCHH!!!<br />';
}
} /*** end of class ***/
/*** declare our interface ***/
interface testdrive{
/*** some functions that must be implemented ***/
function drive();
function stop();
}
/*** an new vehicle object ***/
$object = new vehicle;
/*** call some methods ***/
$object->drive();
$object->stop();
?>
You may of course create multiple classes to implement your interface, but they will not inherit from each other. When you inherit from a parent class, you may choose to override some of parent methods. If you had multiple parent class methods with the same name, but different functionality or charactaristics, PHP would have no way of telling which of these methods to use. This is why multiple inheritance does not work in PHP. In contrast, classes that implement an interface, must implement every method so there is no ambiguity.
In the real world interfaces provide us with the tools harness parts of multiple classes. Consider this scenario. If we had two classes, one for a fax and the other for a printer. Each has seperate uses and could be described like this:
<?php
class fax{
public function dial();
public function send();
public function recieve();
}
class printer{
public function printBlack();
public function printColor();
public function printDraft();
}
?>
Both of the above classes give the required usage for each item, but they do not take into consideration the existance of a printer/fax machine. To get the usage of both classes we would do something like this:
<?php
class fax{
public function dial();
public function send();
public function recieve();
}
class printer extends fax{
public function printBlack();
public function printColor();
public function printDraft();
public function kick();
}
class printerFax extends fax{
}
$object = new printerFax;
?>
This code works by creating a stack of classes. The grandparent class is fax. Then the printer class extends the fax class and inherits all the methods from that class. This is where some problems may arise. The printer class now has the function dial() available to it which is clearly going to cause some confusion and possibly errors in logic.
To counter this problem an interface can be used to tell the classes what functions (methods) are required. Lets look at the design.
<?php
interface fax{
public function dial();
public function send();
public function recieve();
}
interface printer{
public function printBlack();
public function printColor();
public function printDraft();
public function kick();
}
class printerFax implements fax, printer{
public function dial(){ }
public function send(){ }
public function recieve(){ }
public function printBlack(){ }
public function printColor(){ }
public function printDraft(){ }
public function kick(){ }
}
$object = new printerFax;
?>
Before we go further, it is recommended you run the above code. It will produce no output but we need to be sure all is well. Having run the code, remove the line
public function kick(){ }
and run it again. What you should now get is an error such as:
Fatal error: Class printerFax contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (printer::kick) in /www/oop.php on line 22
With the kick() function removed from our implementation, we have essentially broken the contract that says we will implement every function (method) specified in the interface. We can gather these functions fractionally from multiple classes, but we MUST have them all or we will get errors such as the one above.
Interfaces play a major role in with SPL and it is recommend you implement the interfaces from SPL and not just the class methods.
PHP has available several class functions to help you through the OOP mine field.
Each of these is shown here beginning with the get_declared_interfaces().
This helper function provides an array of all the available declared interfaces.
<?php
interface fax{
public function dial();
public function send();
public function recieve();
}
interface printer{
public function printBlack();
public function printColor();
public function printDraft();
public function kick();
}
/*** our interface implementation ***/
class printerFax implements fax, printer{
public function dial(){ }
public function send(){ }
public function recieve(){ }
public function printBlack(){ }
public function printColor(){ }
public function printDraft(){ }
public function kick(){ }
}
/*** create and printerfax object ***/
$object = new printerFax;
/*** get the declared interfaces ***/
foreach(get_declared_interfaces() as $key=>$interface)
{
echo $key.' => '.$interface.'<br />';
}
?>
The above code should produce a list such as this:
From the list above you can see the SPL interfaces available and at the bottom is our fax and printer interfaces. The printerfax is not listed as it is not an interface, rather it is an implentation of an interface.
Here we will see three helper functions for our classes
<?php
/*** a pretend class ***/
class fax{
public function dial(){ }
public function send(){ }
public function recieve(){ }
}
/*** another pretend class ***/
class printer{
public function printBlack(){ }
public function printColor(){ }
public function printDraft(){ }
public function kick(){ }
}
/*** create an instance of the fax class ***/
$foo = new fax;
/*** create an instance of the printer class ***/
$bar = new printer;
echo '$foo is from the ' get_class($foo).' class<br />';
echo class_exists("printer").'<br />';
echo 'Declared classes are:<br /> ';
foreach(get_declared_classes() as $key=>$classname)
{
echo $key.' -> '.$classname.'<br />';
}
?>
The little snippet above will produce over one hundred available classes, shortened here for the sake of sanity, such as these below. Note our fax and printer classes at the bottom of the list.
Earlier in this tutorial we stated that the class definition must be included in every call to an object. This is commonly achieved with the include() or require() functions such as below.
<?php
/*** include our class definitions ***/
include('classes/vehicle.class.php');
include('classes/motorcycle.class.php');
include('classes/printer.class.php');
include('classes/printer.class.php');
/*** instantiate a new vehicle class object ***/
$vehicle = new vehicle;
*** instantiate a new motorcycle class object ***/
$bike = new motorcycle;
*** instantiate a new printer class object ***/
$printer = new printer;
*** instantiate a new fax class object ***/
$fax = new fax;
?>
<?php
/*** Autoload class files ***/
function __autoload($class){
require('classes/' . strtolower($class) . '.class.php');
}
/*** instantiate a new vehicle class object ***/
$vehicle = new vehicle;
/*** instantiate a new motorcycle class object ***/
$bike = new motorcycle;
/*** instantiate a new printer class object ***/
$printer = new printer;
/*** instantiate a new fax class object ***/
$fax = new fax;
?>
Now we can load up as many class definitions as we like because they will be autoloaded when we try to use a class that has not been defined. This can save much coding and much searching for code. It is important to remember the naming convention of your classes and class files. Each class file should be named the same as the class definition itself. eg: a class definition file named fax would have the filename fax.class.php
The use of the strtolower() function assures compatibility of naming conventions as windows machines fail to be case sensitive for filenames.
We have seen a lot of code above for the use of objects and how they can save us time (and $$$) by re-using them. But what if we needed to somehow store an object for later retrieval, perhaps in a database or in a session variable? PHP has given us the serialize() function to make this rather effortless. There are some limitations, but this can be a very useful tool for applications. Lets see how it performs with a little code.
<?php
/*** code here ***/
?>
Comes a time in every programmers life when...hmm
Overloading in PHP has caused much confusion for no real reason. PHP Overloading can be broken downinto two basic components
Simply put, Method Overloading is achieved by a special function named __call(). It is available as a sort of method wildcard for calls to undefined methods within a class. This special function is only called when the original method name does not exist. The __call() will only work when the class method you are trying to access does not exist. Lets take it for a spin..
<?php
class my_class{
public function foo() {
return "This is the foo function";
}
} /*** end of class ***/
/*** create a new class object ***/
$obj = new my_class;
/*** call a non-existant method ***/
$obj->bar();
?>
Of course the above snippet of code will produce an error such as
Fatal error: Call to undefined method my_class::bar() in /www/overload.php on line 12
because we have called the bar() class method that does not exist. Enter __call(). With the __call() function in place, PHP will try to create the function and you have any code within the _call() method that you like. The __call() method takes two arguements, the method name, and the arguements. Your call to the undefined method may have many arguements and these are returned in an array. Lets put it to the test with two args.
<?php
class my_class{
public function foo() {
return "This is the foo function";
}
/*** __call() method with two args ***/
public function __call($method, $arg){
echo $method.'<br />';
print_r($arg);
}
} /*** end of class ***/
/*** create a new class object ***/
$obj = new my_class;
/*** call a non-existant method ***/
$obj->bar("arg1", "arg2");
?>
The above code will print the following
bar
Array ( [0] => arg1 [1] => arg2 )
The __call() method has returned the method name that we called along with the array of args passed to it.
Lets now look at we can dynimically manipulate or overload our data.
<?php
class readyGetSet {
/*** declare $item ***/
private $item = 'Skate Board';
/*** declare the price ***/
private $price = 100;
/*** our call function ***/
function __call($method, $arguments){
/*** set property and prefix ***/
$prefix = strtolower(substr($method, 0, 3));
$property = strtolower(substr($method, 3));
if (empty($prefix) || empty($property))
{
return;
}
if ($prefix == 'get' && isset($this->$property))
{
return $this->$property;
}
if ($prefix == 'set')
{
$this->$property = $arguments[0];
}
}
}
$obj = new readyGetSet;
echo 'Item: ' . $obj->getItem() . '<br />';
echo 'Price: ' . $obj->getPrice() . '<br />';
$obj->setItem('CD');
$obj->setPrice(25);
echo 'Item: ' . $obj->getItem() . '<br />';
echo 'Price: ' . $obj->getPrice() . '<br />';
?>
The second part of overloading refers to properties and the ability to be able to dynamically get and set object properties. The __get() function is called when reading the value of an undefined property, and __set() is called when trying to change that properties value. I hope this is clear as it can get a little confusing... Lets see how it works by example.
<?php
class candy{
/*** declare a property ***/
public $type='chocolate';
/*** a normal method ***/
public function wrap(){
echo 'Its a wrap';
}
/*** our __set() function ***/
public function __set($index, $value){
echo 'The value of '.$index.' is '.$value;
}
} /*** end of class ***/
/*** a new candy object ***/
$candy = new candy;
/*** set a non existant property ***/
$candy->bar = 'Blue Smarties';
?>
The result from above will be:
The value of bar is Blue Smarties
Lets see what we have done. We have described a class named candy which contains a public property named $type. It has a simple method and our __set() method. After the class our user code creates a new instance of the candy class. Then we try to set a variable that does not exist in the class. Here the __set method takes control and assigns it for us. We then see in our __set method that it echoes the name of the variable, plus its intended value. The __set() method takes two arguements, the name of the non existant variable, and its intended value.
The __get() method ....
<?php
class candy{
/*** declare a property ***/
public $type='chocolate';
public $choctype = array('milk'=>0, 'dark'=>1, 'plain'=>2);
/*** a normal method ***/
public function wrap(){
echo 'Its a wrap';
}
/*** our __set() function ***/
public function __get($index){
echo 'Retrieving element of $choctype property with index of '.$index.'<br />';
return $this->choctype[$index];
}
} /*** end of class ***/
/*** a new candy object ***/
$candy = new candy;
/*** set a non existant property ***/
echo 'The value of the following element property is '.$candy->milk;
?>
You have more than likely seen the use standard constants in PHP. To define a standard constant we use this code:
/*** define an error message ***/
define('_ERROR_MSG', 'An Error has occured!');
/*** echo the constant ***/
echo _ERROR_MSG;
?>
The above snippit would output
An Error has occured!
To define a class constant we use the const keyword.
<?php
class my_class {
/*** define a class constant ***/
const _ERROR_MSG = 'An Error has occured!';
public function show(){
echo self::_ERROR_MSG;
}
} /*** end of class ***/
?>
<?php
/*** static call to constant ***/
echo my_class::_ERROR_MSG;
/*** instantiate a class object ***/
$my_class = new my_class;
/*** can run the show() method ***/
$my_class->show();
/*** static call to the show method() ***/
my_class::show();
?>
Each of the above methods would output the same line
An Error has occured!
A class constant, like standard constants, must be exactly as the name suggests, a constant value. It cannot be a variable or the result of a function or method.
Okay, show of hands out there - who else is tired of the boring old car analogies when it comes to talking about object-oriented programming in PHP? I have to admit; even I got a little sick of reading them after a bit. It seemed like there wasn't much originality behind them, and several of them just assumed that you understood what "$this->car_name" was.
So, here we go with something a little bit different - hopefully it'll turn out to be something useful for all of you developers out there trying to wade through the wide world of object-oriented programming with PHP.
What's so cool about OOP anyway?
Well, let's start at the beginning and lay down some basic terms to get things started. First off, most PHP developers write when their first coming into the language is called "procedural". In this kind of code, one thing happens after another and the most exciting thing that could happen is the inclusion of another file. Functions are scattered here and there, and a library of them may even be used to help move things along a bit faster. There are limitations to this kind of programming, though. Procedural code tends to get pretty unwieldy pretty quickly when working with larger site. Shifting things around to included files helps, but it doesn't get to the root of the problem.
Object-oriented programming can help with all of this. Let's back up just a second and talk about what the "object" part in that term means. Objects are variable types in PHP that can do all sorts of fun things. They can be passed around from place to place all while maintaining all of their properties and methods inside. If that doesn't make sense to you yet, hang with me a bit, I'm going to help. The first step is to discover how to create an object of your very own.
The Object of Our Affections
Objects are really just a fancy variable type (as mentioned above) with some nifty features that come along with them. To create an object, you'll need something called a class. Think of a class as the framework behind an object that defined the functionality and variables to keep inside. Here's an example:
<?php
class myClass {
function myClass(){
}
}
?>
In this case, "myClass" is, well, the name of the class and the word "class" is a keyword that PHP looks at to know what you're doing. Right inside the class definition, there's a function, "myClass". Now, I'm not trying to confuse you on purpose - there's a reason why it's named the same as the class. It's a special kind of function called the constructor. Just like laying the foundation and putting up the walls of a new building is part of constructing it, our "myClass" function is run when the object is first created.
Ah! Now to the fun part! Object creation! (Well, not so much fun as the next step in the process).
So, we have our little sample class above sitting there, ready to use. But, to be able to get to anything inside it, we need to make an object that represents it. Here's an example:
<?php
$mine=new myClass();
?>
Man that's hard work...well, okay - so it's not, but there's still a little there to explain. The variable "$mine" is the newborn object. If you do a print_r() on it (you do know about print_r, don't you?), you can see that it's a little bit special. To tell PHP that we want to make it an object, we use the "new" keyword along with the name of the class. Our example above doesn't really do anything yet, but that's about to change when we introduce properties.
Putting Properties Into the Mix
Like everything else involved with classes, properties are really just something you already know (and love). Properties are just variables in disguise. Why are they different? Well, Inside of a class, you can have variables, but there are some variables that ascribe to a higher calling. These variables can be accessed both inside and outside of the class and are global inside an object. Want an example? Here's a simple one:
<?php
class myClass {
var $my_var = 'testing';
function myClass(){
}
}
$mine=new myClass();
echo $mine->my_var;
?>
In our example above, we're using the same class structure as before, but we've added something different. The "$my_var" variable defined at the top puts that value out where we can get to it later. Later comes around when, after creating the object, we have some fun with a new operator entering the game, the "->" (or as I usually call it, the arrow). Basically, this tells PHP that the variable you're referencing is a part of the "$mine" object. PHP automatically pulls the current value from the object and echoes it out just like any other value. And this isn't limited to just variables, either - you can use the arrow to call methods too (functions in a class, remember), like so:
<?php
class myClass {
function myClass(){
}
function echoMe(){
echo 'me';
}
}
$mine=new myClass();
$mine->echoMe();
?>
Running this script will result in the text "me" being output to the page. Pretty simple, huh?
Taking the Next Step
Since we're starting to get a bit more complex anyway, why don't we apply all of this great knowledge that we've already accumulated into something a bit more useful - like a simple graphical example. In this example we're going to create a box on the page (a DIV tag) and with the help of PHP and some CSS, change a few things about it. But first, the code:
<?php
class myHappyBox {
var $box_height = 100;
var $box_width = 100;
var $box_color = '#EC0000';
function myHappyBox(){
}
function setHeight($value){
$this->box_height=$value;
}
function setWidth($value){
$this->box_width=$value;
}
function setColor($value){
$this->box_color=$value;
}
function displayBox(){
echo sprintf('
<div style="height:%spx;width:%spx;background-color:%s"> </div>
',$this->box_height,$this->box_width,$this->box_color);
}
}
$box=new myHappyBox();
$box->displayBox();
?>
Now, don't let this code scare you off, it's really not that complex. There's a few new things to look at in here, but nothing that doesn't make sense with the right explanation. We know that we're going to be building a box with this class, so we know that the box is going to have certain properties - height, width, and a color. Looking at the class above, you can see those three settings defined as properties with default values. By defining them there at the top, we have settings to fall back on if we do like the example shows and just call displayBox(). As it stands, the example will show a 100 pixel by 100 pixel DIV with a red background. This is all well and good, but what happens if we want to change one of these settings? Well, that's what the other functions are for.
There are three "set" functions in our myHappyBox class - one for height, one for width, and one for the background color - and they all work the same basic way. Each of them takes in a value and sets the global (to the object) property to the new value. So, if we wanted to change the size of the box, we could do:
<?php
$box=new myHappyBox();
$box->setHeight(30);
$box->setWidth(300);
$box->displayBox();
?>
The above code would then alter our default box and display one that's a whole lot wider than it is tall. The same kind of change can be made with the setColor method, giving it a value of an HTML color (hex).
Wrapping it all up
So, that's basically it - not really anything to be scared of or to avoid for the future. In fact, object-oriented programming can be one of the better things to happen to you and your code. Sure, rewriting that application you're currently on in a more "OOP fashion" might be a big pain, but there's always the next project to consider. And remember, there's more to working with objects, classes, methods, properties, blah, blah, blah than what I've said here. You should definitely head over to the PHP.net site and check out their great resource on the topic. It has the answers to the questions you'll want to know now that you're finished with this little tutorial.
by: Chris Cornutt
