This PPT gives information about:
Advanced Theories
Inheriting Classes
Inheriting Constructors and Destructors
Overriding Methods
Access Control
Using the Scope Resolution Operator
Creating Static Members
Abstract Classes and Methods
If you are new to programing in general OR if you started programing in php before Object-Oriented Programming was even available, this presentation is designed to help you get up to speed on Object-Oriented terminology and give you practical skills as well as resources to continue learning.
This PPT gives information about:
Advanced Theories
Inheriting Classes
Inheriting Constructors and Destructors
Overriding Methods
Access Control
Using the Scope Resolution Operator
Creating Static Members
Abstract Classes and Methods
If you are new to programing in general OR if you started programing in php before Object-Oriented Programming was even available, this presentation is designed to help you get up to speed on Object-Oriented terminology and give you practical skills as well as resources to continue learning.
This ppt gives information about:
1. OOPs Theory
2. Defining a Class
3. Creating an Object
4. The $this Attribute
5. Creating Constructors
6. Creating Destructors
For beginners who want to go to the next level of OOP in PHP, we talk about magic methods, iterators, filters, some parts of the SPL, the subject/observer pattern and how you can build classes that have a lot of power and responsibility by implementing interfaces and then type-hinting and using just methods that are defined in the interface. Prefer composition over inheritance.
This ppt gives information about:
1. OOPs Theory
2. Defining a Class
3. Creating an Object
4. The $this Attribute
5. Creating Constructors
6. Creating Destructors
For beginners who want to go to the next level of OOP in PHP, we talk about magic methods, iterators, filters, some parts of the SPL, the subject/observer pattern and how you can build classes that have a lot of power and responsibility by implementing interfaces and then type-hinting and using just methods that are defined in the interface. Prefer composition over inheritance.
Abstraction, Encapsulation, Polymorphism, and Interfaces: whether you’ve been programming in PHP for years or are just starting your journey, these terms can be overwhelming even on a good day. Variables, conditionals, those all make sense. But this whole Object-Oriented thing is WAY more complicated. Not only that, people that already understand it act like it’s so easy and they talk right over the simple questions and never explain the basic concepts in a way that actually makes sense. In this session we’ll take you through real life examples of Object-Oriented terminology in a way that will make sense of all the mumbo jumbo and allow you to utilizing OOP immediately.
The recent Project of the Month on SourceForge, XOOPS (http://www.xoops.org) was designed from the very beginning as an object-oriented CMS, which is even reflected in its name: eXtensible Object Oriented Portal System. Michael will present the OOP oriented architecture of XOOPS, and show how OOP makes development of XOOPS modules easy and fun, promotes reuse of code, while keeping GUI consistent across all modules.
Object oriented programming assume everything as an object
Class − This is a programmer-defined data type, which includes local functions as well as local data.
Object − An individual instance of the data structure defined by a class.
Member Variable − These are the variables defined inside a class.
Member function − These are the function defined inside a class and are used to access object data.
Inheritance − When a class is defined by inheriting existing function of a parent class then it is called inheritance.
Parent class − A class that is inherited from by another class. This is also called a base class or super class.
Child Class − A class that inherits from another class. This is also called a subclass or derived class.
Polymorphism − This is an object oriented concept where same function can be used for different purposes. For example function name will remain same but it take different number of arguments and can do different task.
Data Abstraction − Any representation of data in which the implementation details are hidden (abstracted).
Encapsulation − refers to a concept where we encapsulate all the data and member functions together to form an object.
Constructor − refers to a special type of function which will be called automatically whenever there is an object formation from a class.
Destructor − refers to a special type of function which will be called automatically whenever an object is deleted or goes out of scope.
....
Demystifying Object-Oriented Programming - PHP UK Conference 2017Alena Holligan
Abstraction, Encapsulation, Polymorphism, and Interfaces: whether you’ve been programming in PHP for years or are just starting your journey, these terms can be overwhelming even on a good day. Variables, conditionals, those all make sense. But this whole Object-Oriented thing is WAY more complicated. Not only that, people that already understand it act like it’s so easy and they talk right over the simple questions and never explain the basic concepts in a way that actually makes sense. In this session we’ll take you through real life examples of Object-Oriented terminology in a way that will make sense of all the mumbo jumbo and allow you to utilizing OOP immediately.
Abstraction, Encapsulation, Polymorphism, and Interfaces: whether you’ve been programming in PHP for years or are just starting your journey, these terms can be overwhelming even on a good day. Variables, conditionals, those all make sense. But this whole Object-Oriented thing is WAY more complicated. Not only that, people that already understand it act like it’s so easy and they talk right over the simple questions and never explain the basic concepts in a way that actually makes sense. In this session we’ll take you through real life examples of Object-Oriented terminology in a way that will make sense of all the mumbo jumbo and allow you to utilizing OOP immediately.
To better understand the behavior of servlets, let’s take a look at the life cycle of servlets.
A servlet is basically a small Java program that runs within a Web server. It can receive requests from clients and return responses. The whole life cycle of a servlet breaks up into 3 phases:
• Initialization: A servlet is first loaded and initialized usually when it is requested by the corresponding clients. Some websites allow the users to load and initialize servlets when the server is started up so that the first request will get responded more quickly.
• Service: After initialization, the servlets serve clients on request, implementing the ap- plication logic of the web application they belong to.
• Destruction: When all pending requests are processed and the servlets have been idle for a specific amount of time, they may be destroyed by the server and release all the resources they occupy.
More specifically, the behavior of a servlet is described in javax.servlet.Servlet interface, in which the following methods are defined:
• public void init(ServletConfig config) throws ServletException
This method is called once when the servlet is loaded into the servlet engine, before the servlet is asked to process its first request.
The init method has a ServletConfig parameter. The servlet can read its initialization arguments through the ServletConfig object. How the initialization arguments are set is servlet engine dependent but they are usually defined in a configuration file.
A typical example of an initialization argument is a database identifier. A servlet can read this argument from the ServletConfig at initialization and then use it later to open a connection to the database during processing of a request:
private String databaseURL;
public void init(ServletConfig config) throws ServletException { super.init(config);
databaseURL = config.getInitParameter("database");
}
• public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException
This method is called to process a request. It can be called zero, one or many times until the servlet is unloaded.
Once a servlet is loaded, it remains in the server’s memory as a single object instance. Thereafter, the server invokes the servlet to handle a request using a simple, lightweight method invocation. Unlike with CGI, there’s no process to spawn or interpreter to invoke, so the servlet can begin handling the request almost immediately. Multiple, concurrent requests are handled by separate threads, so servlets are highly scalable.
Servlets are naturally enduring objects. Because a servlet stays in the server’s memory as a single object instance, it automatically maintains its state and can hold on to external resources, such as database connections, that may otherwise take several seconds to establish. The following servlet presents information about how many times it has been accessed:
To better understand the behavior of servlets, let’s take a lo
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All of this illustrated with link prediction over knowledge graphs, but the argument is general.
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Session Overview
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Synapseindia object oriented programming in php
1. Object oriented programming in PHP
• PHP, like most modern programming languages (C++, Java, Perl, JavaScript, etc.),
supports the creation of objects.
• Creating an object requires you to first define an object class (containing variables
and/or function definitions) and then using the “new” keyword to create an instance of
the object class. (Note that the object must be defined before you instantiate it.)
<?php
// Assume that the "Person" object has been previously defined. . .
$x = new Person; // creates an instance of the Person class (*no* quotes)
// The object type need not be "hardcoded" into the declaration.
$object_type = 'Person';
$y = new $object_type; // equivalent to $y = new Person;
$z = new Vehicle('Jaguar','green'); // creating an object and passing
// arguments to its constructor
?>
2. Defining (declaring) a class
• Use the “class” keyword which includes the class name (case-insensitive, but
otherwise following the rules for PHP identifiers). Note: The name “stdClass” is
reserved for use by the PHP interpreter.
<?php
class Person
{
var $name;
function set_name($new_name) {
$name = $this -> new_name;
}
function get_name() {
return $this -> name;
}
}
• Use the “$this” variable when accessing properties and functions of the current
object. Inside a method this variable contains a reference to the object on which
the method was called.
3. Declaring a class (cont.)
• Properties and functions can be declared as “public” (accessible outside the
object’s scope), “private” (accessible only by methods within the same class), or
“protected” (accessible only through the class methods and the class methods of
classes inheriting from the class.
• Note that unless a property is going to be explicitly declared as public, private, or
protected, it need not be declared before being used (like regular PHP variables).
<?php
class Person
{
protected $name;
protected $age;
function set_name($new_name) {
$name = $this -> new_name;
}
function get_name() {
return $this -> name;
}
}
4. Declaring a class (cont.)
• Classes can also have their own constants defined (using the “const” keyword),
can have their own static properties and functions (using the keyword “static”
before “var” or “function”), and can also can constructors and destructors (see
below).
• Static properties and functions are accessed (see below) using a different format
than usual for objects, and static functions cannot access the objects properties
(i.e. the variable $this is not defined inside of a static function).
<?php
class HTMLtable {
static function start() {
echo "<table> n";
}
static function end() {
echo "</table> n";
}
}
HTMLtable::start();
5. Accessing properties and methods
• Once you have an object, you access methods and properties (variables) of the
object using the -> notation.
<?php
$me = new Person;
$me -> set_name('Russ');
$me -> print_name();
$name = $me -> get_name();
echo $me -> get_name();
$age = 36;
$me -> set_age($age);
?>
6. Constructors and destructors
• Constructors are methods that are (generally) used to initialize the object’s
properties with values as the object is created. Declare a constructor function in an
object by writing a function with the name __construct().
<?php
class Person {
protected $name;
protected $age;
function __construct($new_name, $new_age) {
$this -> name = $new_name;
$this -> age = $new_age;
}
// . . . other functions here . . .
}
$p = new Person('Bob Jones', 45);
$q = new Person('Hamilton Lincoln', 67);
?>
• Destructors (defined with a function name of __destructor() ) are called when an
object is destroyed, such as when the last reference to an object is removed or the
end of the script is reached (the usefulness of destructors in PHP is limited, since,
for example dynamic memory allocation isn’t possible in the same way that it is in
C/C++).
7. Inheritance
• Use the “extends” keyword in the class definition to define a new object that inherits
from another.
<?php
class Employee extends Person {
var $salary;
function __construct($new_name, $new_age, $new_salary); {
$this -> salary = $new_salary;
parent::__construct($new_name, $new_age); // call the constructor
// of parent object
}
function update_salary($new_salary) {
$this -> salary = $new_salary;
}
$emp = new Employee('Dave Underwood', 25, 25000);
?>
8. Inheritance (cont.)
• The constructor of the parent isn’t called unless the child explicitly references it (as
in this previous case). There is no automatic chain of calls to constructors in a
sequence of objects defined through inheritance.
• You could “hard-code” the call to the parent constructor using the function call
“Person::__construct($new_name, $new_age);” but it’s typically better to define
it in the manner given using the parent::method() notation. The same manner is
used to call the method of a parent that has been overridden by its child.
• You can use the “self” keyword to ensure that a method is called on the current
class (if a method might be subclassed), in this style self::method();
• To check if an object is of a particular class, you can use the instanceof
operator.
if ($p instanceof Employee) {
// do something here
}
9. More on classes
• You can also define interfaces for objects (for which any object that uses that
interface must provide implementations of certain methods), and you can define
abstract classes or methods (that must be overridden by its children).
• The keyword “final” can be used to denote a method that cannot be overridden by
its children.
class Person {
var $name;
final function get_name() {
return $this -> name;
}
}
10. More on classes (cont.)
• There are methods for “introspection” about classes, i.e. the ability of a program to
examine an object’s characteristics.
For example, the function class_exists() can be used (surprise!) to determine
whether a class exists or not.
The function get_declared_classes() returns an array of declared classes.
$classes = get_declared_classes();
You can also get an array of method names in any of the following (equivalent)
manners:
$methods = get_class_methods(Person);
$methods = get_class_methods('Person');
$class = 'Person';
$methods = get_class_methods($class);
11. More introspection functions
• There are a wide variety of introspection functions, several more are listed below.
get_class_vars($object); /* gets an associative array that maps
property names to values (including
inherited properties), but it *only*
gets properties that have default
values (those initialized with
simple constants) */
is_object($object); // returns a boolean value
get_class($object); /* returns the class to which an object
belongs */
method_exists($object, $method); // returns a boolean value
get_object_vars($object); /* returns an associative array
mapping properties to values (for
those values that are set (i.e.
not null) */
12. A word about object methods…
• When defining the names of your own object methods, you should generally avoid
starting them with a double underscore. Why?
• There are some “built-in” or predefined PHP method names that start in this
manner, most notably constructors and destructors using the __construct() and
__destructor() names. In the future (in new versions of PHP), it’s possible that
further methods might be defined that begin with a double underscore.
• Other reserved method names include __sleep() and __wakeup() which are used
for object serialization and __get() and __set(), which can be defined so that if you
try to access an object property that doesn’t exist, these methods give an
opportunity to either retrieve a value or set the (default?) value for that property.
For example, if a class is used to represent data obtained from a database, you
could write __get() and __set() methods that read and write data whenever
requested.
13. PHP sessions
• By default, HTML and web servers don’t keep track of information entered on a
page when the client’s browser opens another page. Thus, doing anything
involving the same information across several pages can sometimes be difficult.
• Sessions help solve this problem by maintaining data during a user’s visit, and can
store data that can be accessed from page to page in your site.
• You can use session variables for storing information (this is one way that a
“shopping cart” function can work for an online shop, for example).
• Servers keep track of users’ sessions by using a session identifier, which is
generated by the server when a session starts and is then used by the browser
when it requests a page from the server. This session ID can be sent through a
cookie (the default behavior) or by passing the session ID in the URL string.
• Sessions only store information temporarily, so if you need to preserve information,
say, between visits to the same site, you should likely consider a method such as
using a cookie or a database to store such information.
14. PHP sessions (cont.)
• To start a session, use the function session_start() at the beginning of your PHP script
before you store or access any data. For the session to work properly, this function
needs to execute before any other header calls or other output is sent to the browser.
<?php
session_start();
?>
<!DOCTYPE html PUBLIC "-//Www//DTD XHTML 1.0 Transitional//EN"
"http://www.abc.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.abc.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Session example</title>
</head>
<body>
<?php
include_once ('object.php'); // Includes definition of the Person class
$_SESSION['hello'] = 'Hello world';
echo $_SESSION['hello'] . "<br/><br/>n";
$_SESSION['one'] = 'one';
$_SESSION['two'] = 'two';
$me = new Person("Russ", 36, 2892700);
$_SESSION['name'] = $me->get_name();
echo "Testing " . $_SESSION['one'] .", " . $_SESSION['two'] . ", " . $me-
>get_number() . " . . .<br/>n";
?>
</body></html>
view the output page
15. Using session variables
• Once a session variable has been defined, you can access it from other pages.
<?php
session_start();
?>
<!DOCTYPE html PUBLIC "-//abc//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.abc.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Session example 2</title>
</head>
<body>
<?php
echo "Welcome to a new page ". $_SESSION['name'] "!<br/>n";
echo "Hope you enjoy your stay! <br/>";
?>
<p>Back to regular HTML text...
</p>
</body>
</html> view the output page
16. More on session variables
• You need to include a call to the session_start() function for each page on which
you want to access the session variables.
• A session will end once you quit the browser (unless you’ve set appropriate
cookies that will persist), or you can call the session_destroy() function. (Note,
however, even after calling the session_destroy() function, session variables are
still available to the rest of the currently executing PHP page.)
• The function session_unset() removes all session variables. If you want to remove
one variable, use the unset($var) function call.
• The default timeout for session files is 24 minutes. It’s possible to change this
timeout.
17. Deleting all session variables
<?php
session_start();
?>
<!DOCTYPE html PUBLIC "-//abc//DTD XHTML 1.0 Transitional//EN"
"http://www.abc.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.abc.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Session example 3</title>
</head>
<body>
<?php
echo "Deleting all session variables using session_unset(); <br/>n";
session_unset();
echo "Now the session variables are gone. <br/>n";
if (isset($_SESSION['name']))
{ echo $_SESSION['name'] . "<br/>n"; }
else
{ echo "Session variable is not here."; }
?>
</body>
</html>
view the output page
18. Learning Outcomes
• A (very, very brief) introduction to objects in PHP. If you
wish to use objects, then many books on PHP include more
information, and, of course, much information is available
online.
• Sessions are useful for persistence of variables across
many webpages without the need to submit information via
forms.