OOP in PHP.pptx

Define
 Classes : Blue print for any project
 Object : An object is a specific instance of a
class
 Characteristics : the characteristics of a class
or object are known as its properties .
 Method : The behaviors of a class — that is,
the actions associated with the class — are
known as its methods .

Create a PHP class
<?php
class person {
}
?>

Add Data to Class
<?php
class person {
var $name;
}
?>

Add Function/Method to class
<?php
class person {
var $name;
function set_name($new_name) {
$this->name=$new_name;
}
function get_name() {
return $this->name;
}
}
?>

Include in Main file
<?php
include(“Class_lib.php”);
?>

Create Object
<?php
$stefan=new person();
$jimmy=new person();
?>

Set Object Properties
<?php
$stefan->set_name("Stefan Mischook");
$jimmy->set_name("Nick Waddles");
?>

Accessing an Objects Data
<?php
echo "Stefan's full name: " . $stefan->get_name();
echo "Nick's full name: " . $jimmy->get_name();
?>

Don’t Access Property Directly
• Bad Example
<?php
echo "Stefan's full name: " . $stefan->name;
?>

Constructor
<?php
class person {
var $name;
function __construct($person) {
$this->name=$person
}
function set_name($new_name) {
$this->name=$new_name;
}
function get_name() {
return $this->name;
}
}
?>

<?php
$stefan=new person("Stefan Mischook");
echo "Stefan's full name: " . $stefan->
get_name();
?>

Access Modifier
• Public properties can be accessed by any code, whether
that code is inside or outside the class. If a property is
declared public, its value can be read or changed from
anywhere in your script.
• Private properties of a class can be accessed only by
code inside the class. So if you create a property that ’ s
declared private, only methods inside the same class
can access its contents. (If you attempt to access the
property outside the class, PHP generates a fatal error.)
• Protected properties are a bit like private properties in
that they can ’ t be accessed by code outside the class,
but there ’ s one subtle difference: any class that
inherits from the class can also access the properties.

Reusing the code : Inheritance
<?php
class employee extends person {
//Extends is the keysword used for inheritance
function __construct($ename)
{
$this->name=$ename;
}
}
?>

<?php
$jimmy=new employee(“Johnes fingers");
echo “jimmy's full name: " . $jimmy->
get_name();
?>

Overriding Method
<?php
class employee extends person {
//Extends is the keysword used for inheritance
function __construct($ename)
{
$this->name=$ename;
}
}
protected function set_name($new_name) {
if ($new_name == "Stefan Lamp") {
$this->name = $new_name;!
}?>

Working with __get() __set() __call()
Method
• PHP allows you to create three “ magic ” methods
that you can use to intercept property and
method accesses:
• _get() is called whenever the calling code
attempts to read an invisible property of the
object
• _set() is called whenever the calling code
attempts to write to an invisible property of the
object
• _call() is called whenever the calling code
attempts to call an invisible method of the object

What is meant by “ invisible ” ?
• In this context, invisible means that the
property or method isn ’ t visible to the calling
code. Usually this means that the property or
method simply doesn ’ t exist in the class, but
it can also mean that the property or method
is either private or protected, and hence isn ’ t
accessible to code outside the class.

Example of __get()
class Car {
public function __get( $propertyName ) {
echo “The value of ‘$propertyName’ was requested ”;
return “blue”;
}
}
$car = new Car();
$x = $car- > color; // Displays “The value of ‘color’ was
requested”
echo “The car’s color is $x ”; // Displays “The car’s
color is blue”

• Similarly, to catch an attempt to set an
invisible property to a value, use _set() .
• Your _set() method needs two parameters:
the property name and the value to set it to. It
does not need to return a value:
public function __set( $propertyName,
$propertyValue ) {
//Do what ever u want to do here
}

Example
<?php
class Car {
private $_extradata=array();
public function __set($propertyName, $propertyValue ) {
$this-> _extraData[$propertyName] = $propertyValue;
}
}
$car = new Car;
$car->color="red";
print_r($car);
?>

• Just as you can use _get() and _set() to handle reading and
writing nonexistent properties.
• you can also use _call() to handle calls to nonexistent
methods of a class.
• Just create a method named _call() in your class that
accepts the nonexistent method name as a string, and any
arguments passed to the nonexistent method as an array.
• The method should then return a value (if any) back to the
calling code:
public function __call( $methodName, $arguments ) {
// (do stuff here)
return $returnVal;
}

Example
<?php
class Car {
public function __call($MethodName, $argument) {
echo "The value of '$MethodName' was requested ";
return $argument[0];
}
}
$car = new Car;
$x = $car-> color("red");
echo "The car's color is $x ";
?>

Other Magic Method
• _isset() is called whenever the calling code
attempts to call PHP ’ s isset() function on an
invisible property. It takes one argument —
the property name — and should return true
if the property is deemed to be “ set, ” and
false otherwise:

Example
class MyClass {
public function __isset( $propertyName ) {
// All properties beginning with “test” are “set”
return ( substr( $propertyName, 0, 4 ) == “test” ) ? true : false;
}
}
$testObject = new MyClass;
echo isset( $testObject- > banana ) . “ ”; // Displays “”
(false)
echo isset( $testObject- > testBanana ) . “ ”; //
Displays “1” (true)

• __unset() is called when the calling code
attempts to delete an invisible property with
PHP ’ s unset() function. It shouldn ’ t return a
value, but should do whatever is necessary to
“ unset ” the property (if applicable):

Example
class MyClass {
public function __unset( $propertyName ) {
echo “Unsetting property ‘$propertyName’ 
”;
}
}
$testObject = new MyClass;
unset( $testObject- > banana ); // Displays
“Unsetting property ‘banana’”

• __callStatic() works like _call() , except that it is called whenever an
attempt is made to call an invisible static method. For example:
class MyClass {
public static function __callStatic( $methodName, $arguments ) {
echo “Static method ‘$methodName’ called with the arguments: ”;
foreach ( $arguments as $arg ) {
echo “$arg ”;
}
}
}
MyClass::randomMethod( “apple”, “peach”, “strawberry” );

Storing Object as a String
• Objects that you create in PHP are stored as
binary data in memory. Although you can pass
objects around using PHP variables, functions,
and methods, sometimes its useful to be able to
pass objects to other applications, or via fields in
Web forms, for example.
• PHP provides two functions to help you with this:
– serialize() converts an object — properties, methods,
and all — into a string of text
– unserialize() takes a string created by serialize() and
turns it back into a usable object

Example
class Person {
public $age;
}
$harry = new Person();
$harry- > age = 28;
$harryString = serialize( $harry );
echo “Harry is now serialized in the following string:
‘$harryString’ ”;
echo “Converting ‘$harryString’ back to an object... ”;
$obj = unserialize( $harryString );
echo “Harry’s age is: $obj- > age ”;

• What ’ s more, when you serialize an object, PHP attempts to call a
method with the name _sleep() inside the object. You can use this
method to do anything that ’ s required before the object is
serialized.
• Similarly, you can create a _wakeup() method that is called when
the object is unserialized.
• _sleep() is useful for cleaning up an object prior to serializing it, in
the same way that you might clean up in a destructor method. For
example, you might need to close database handles, files, and so
on.
• In addition, _sleep() has another trick up its sleeve. PHP expects
your _sleep() method to return an array of names of properties to
preserve in the serialized string. You can use this fact to limit the
number of properties stored in the string — very useful if your
object contains a lot of properties that you don ’ t need to store.

Example
class User {
public $username;
public $password;
public $loginsToday;
public function __sleep() {
// (Clean up; close database handles, etc)
return array_keys( get_object_vars( $this ) );
}
}

Example
class User {
public function __wakeup() {
echo “Yawn... what’s for breakfast? ”;
}
}
$user = new User;
$userString = serialize( $user );
$obj = unserialize( $userString );

OOP in PHP.pptx

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