Object oriented programming in php 5
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The document provides an overview of object-oriented programming in PHP 5. It discusses key OOP concepts like classes, inheritance, properties, methods, abstraction, interfaces, traits, overloading, and iteration. New features in PHP 5 like visibility, abstract classes, interfaces, cloning and type hinting are also covered at a high level. The document is intended to introduce developers to OOP in PHP 5.
![CLASS
Class name can be any valid label which is a not a
PHP reserved word
A valid class name
starts with a letter or underscore,
followed by any number of
letters, numbers, or underscores
Regular Expression for class name:
[a-zA-Z_x7f-xff][a-zA-Z0-9_x7f-xff]*
A class may contain
constants, variables (called "properties")
and functions (called "methods")
The pseudo-variable $this is available
To call other methods of the same class (within)
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![INHERITANCE : EXTENDS
The keyword extends is used to
inherit the methods and properties of another class
multiple classes inheritance is not allowed
a class can only inherit from one base class
The inherited methods and properties can be overridden
by re-declaring them
Final methods cannot be overridden [final]
Overridden method signature has to be the same
Else E_STRICT error will be triggered
Constructor can be overridden with different parameters
The overridden methods or static properties can be
accessed by referencing them with parent::.
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![CLASSES/OBJECT FUNCTIONS
Table of Contents
call_user_method_array — Call a user method given with an array of parameters
[deprecated]
call_user_method — Call a user method on an specific object [deprecated]
class_alias — Creates an alias for a class
class_exists — Checks if the class has been defined
get_called_class — the "Late Static Binding" class name
get_class_methods — Gets the class methods' names
get_class_vars — Get the default properties of the class
get_class — Returns the name of the class of an object
get_declared_classes — Returns an array with the name of the defined classes
get_declared_interfaces — Returns an array of all declared interfaces
get_object_vars — Gets the properties of the given object
get_parent_class — Retrieves the parent class name for object or class
interface_exists — Checks if the interface has been defined
is_a — Checks if the object is of this class or has this class as one of its parents
is_subclass_of — Checks if the object has this class as one of its parents
method_exists — Checks if the class method exists
property_exists — Checks if the object or class has a property
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![CONSTRUCTOR
PHP 5 constructor:
void __construct ([ mixed $args [, $... ]] )
Parent constructors are not called implicitly
if the child class defines a constructor
parent::__construct() can be used in a child to call
parent constructor
No E_STRICT error message when __construct()
is overridden with different parameters than the
parent __construct()
if PHP 5 cannot find a __construct() function for a
given class, it will search for the old-style
constructor function,
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![EXAMPLE: INTERFACES
// Declare the interface 'iTemplate'
interface iTemplate
{
public function setVariable($name, $var);
public function getHtml($template);
}
// Implement the interface
// This will work
class Template implements iTemplate
{
private $vars = array();
public function setVariable($name, $var)
{
$this->vars[$name] = $var;
}
public function getHtml($template)
{
foreach($this->vars as $name => $value) {
$template = str_replace('{' . $name . '}', $value, $template);
}
return $template;
}
}
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Object oriented programming in php 5
- 1. OBJECT ORIENTED PROGRAMMING IN PHP 5 Sayed Ahmed B.Sc. Engineering in Computer Science & Engineering M. Sc. in Computer Science Exploring Computing for 14+ years [email protected] http://sayed.justetc.net
- 2. WHAT IS NEW IN PHP 5 FOR OOP The Object Model is rewritten to allow for better performance and more features PHP 5 treats objects as references or handles each variable contains an object reference rather than a copy of the entire object See Objects and References In PHP 5 When an object is sent by argument, returned or assigned to another variable the different variables are not aliases: they hold a copy of the identifier (address variable or reference variable) which points to the same object 10/9/2011 2 [email protected]
- 3. WHAT IS NEW IN PHP 5 FOR OOP PHP 5 has a full object model PHP 5 added Visibility (private, public, protected) abstract classes and final classes and methods PHP 5 added additional magic methods interfaces cloning typehinting 10/9/2011 3 [email protected]
- 4. CLASS Example <?php class SimpleClass{ // property declaration public $var = 'a default value'; // method declaration public function displayVar() { echo $this->var; } } ?> 10/9/2011 4 [email protected]
- 5. CLASS Class name can be any valid label which is a not a PHP reserved word A valid class name starts with a letter or underscore, followed by any number of letters, numbers, or underscores Regular Expression for class name: [a-zA-Z_x7f-xff][a-zA-Z0-9_x7f-xff]* A class may contain constants, variables (called "properties") and functions (called "methods") The pseudo-variable $this is available To call other methods of the same class (within) 10/9/2011 5 [email protected]
- 6. CREATE OBJECTS, CREATE INSTANCES OF CLASSES new the new keyword must be used to create an instance of a class If the class is in a namespace its fully qualified name must be used $instance = new SimpleClass(); A copy of an already created object can be made by cloning it 10/9/2011 6 [email protected]
- 7. INHERITANCE : EXTENDS The keyword extends is used to inherit the methods and properties of another class multiple classes inheritance is not allowed a class can only inherit from one base class The inherited methods and properties can be overridden by re-declaring them Final methods cannot be overridden [final] Overridden method signature has to be the same Else E_STRICT error will be triggered Constructor can be overridden with different parameters The overridden methods or static properties can be accessed by referencing them with parent::. 10/9/2011 7 [email protected]
- 8. PROPERTIES Class member variables are called "properties“ Properties are declared with public, protected, or private If declared using var (PHP 4 style), the property will be defined as public However, PHP 5 will generate E_STRICT warning public properties can be accessed everywhere protected properties can be accessed only within the class itself and by inherited and parent classes private properties may only be accessed by the class itself The default visibility is public 10/9/2011 8 [email protected]
- 9. CLASSES/OBJECT FUNCTIONS Table of Contents call_user_method_array — Call a user method given with an array of parameters [deprecated] call_user_method — Call a user method on an specific object [deprecated] class_alias — Creates an alias for a class class_exists — Checks if the class has been defined get_called_class — the "Late Static Binding" class name get_class_methods — Gets the class methods' names get_class_vars — Get the default properties of the class get_class — Returns the name of the class of an object get_declared_classes — Returns an array with the name of the defined classes get_declared_interfaces — Returns an array of all declared interfaces get_object_vars — Gets the properties of the given object get_parent_class — Retrieves the parent class name for object or class interface_exists — Checks if the interface has been defined is_a — Checks if the object is of this class or has this class as one of its parents is_subclass_of — Checks if the object has this class as one of its parents method_exists — Checks if the class method exists property_exists — Checks if the object or class has a property 10/9/2011 9 [email protected]
- 10. CLASS CONSTANTS Classes can have their own constants Interfaces can also have their own constants <?php class MyClass{ const constant = 'constant value'; function showConstant() { echo self::constant . "n"; } } 10/9/2011 10 [email protected]
- 11. CLASS CONSTANTS Example #2 Static data example <?php class foo { // As of PHP 5.3.0 const bar = <<<'EOT' bar EOT; } ?> 10/9/2011 11 [email protected]
- 12. AUTOLOADING CLASSES You may define an __autoload function which is automatically called in case you are trying to use a class/interface which hasn't been defined/included yet spl_autoload_register() provides a more flexible alternative for autoloading classes <?php function __autoload($class_name) { include $class_name . '.php'; } $obj = new MyClass1(); $obj2 = new MyClass2(); ?> 10/9/2011 12 [email protected]
- 13. SPL_AUTOLOAD_REGISTER EXAMPLE <?php class ClassAutoloader { public function __construct() { spl_autoload_register(array($this, 'loader')); } private function loader($className) { echo 'Trying to load ', $className, ' via ', __METHOD__, "()n"; include $className . '.php'; } } $autoloader = new ClassAutoloader(); $obj = new Class1(); $obj = new Class2(); ?> 10/9/2011 13 [email protected]
- 14. CONSTRUCTOR PHP 5 constructor: void __construct ([ mixed $args [, $... ]] ) Parent constructors are not called implicitly if the child class defines a constructor parent::__construct() can be used in a child to call parent constructor No E_STRICT error message when __construct() is overridden with different parameters than the parent __construct() if PHP 5 cannot find a __construct() function for a given class, it will search for the old-style constructor function, 10/9/2011 14 [email protected]
- 15. EXAMPLE #2 CONSTRUCTORS IN NAMESPACED CLASSES <?php namespace Foo; class Bar { public function Bar() { // treated as constructor in PHP 5.3.0-5.3.2 // treated as regular method as of PHP 5.3.3 } } ?> 10/9/2011 15 [email protected]
- 16. DESTRUCTOR void __destruct ( void ) The destructor method will be called as soon as there are no other references to a particular object, or in any order during the shutdown sequence Like constructors parent destructors will not be called implicitly by the engine In order to run a parent destructor one would have to explicitly call parent::__destruct() in the child destructor body The destructor will be called even if script execution is stopped using exit() Exit can be called from destructors to stop execution Throwing exceptions from destructors will cause fatal errors 10/9/2011 16 [email protected]
- 17. SCOPE RESOLUTION OPERATOR (::) is a token that allows access to static constant and overridden properties or methods of a class As of PHP 5.3.0, it's possible to reference the class using a variable $classname = 'MyClass'; echo $classname::CONST_VALUE; // As of PHP 5.3.0 10/9/2011 17 [email protected]
- 18. STATIC KEYWORD Declaring class properties or methods as static makes them accessible without needing an instantiation of the class A property declared as static can not be accessed with an instantiated class object (though a static method can) the pseudo-variable $this is not available inside the method declared as static Static properties cannot be accessed through the object using the arrow operator -> Calling non-static methods statically generates an E_STRICT level warning 10/9/2011 18 [email protected]
- 19. ABSTRACT CLASSES Classes defined as abstract may not be instantiated and any class that contains at least one abstract method must also be abstract Methods defined as abstract simply declare the method's signature - they cannot define the implementation When inheriting from an abstract class all methods marked abstract in the parent's class declaration must be defined by the child additionally, these methods must be defined with the same (or a less restricted) visibility 10/9/2011 19 [email protected]
- 20. ABSTRACT CLASSES abstract class AbstractClass { // Force Extending class to define this method abstract protected function getValue(); abstract protected function prefixValue($prefix); // Common method public function printOut() { print $this->getValue() . "n"; } } class ConcreteClass1 extends AbstractClass { protected function getValue() { return "ConcreteClass1"; } public function prefixValue($prefix) { return "{$prefix}ConcreteClass1"; } } 10/9/2011 20 [email protected]
- 21. OBJECT INTERFACES Interfaces are defined using the interface keyword in the same way as a standard class but without any of the methods having their contents defined Object interfaces allow to create code which specifies which methods a class must implement without having to define how these methods are handled All methods declared in an interface must be public, this is the nature of an interface 10/9/2011 21 [email protected]
- 22. IMPLEMENTING INTERFACES To implement an interface, the implements operator is used Classes may implement more than one interface if desired by separating each interface with a comma A class cannot implement two interfaces that share function names, since it would cause ambiguity Interfaces can be extended like classes using the extends operator The class implementing the interface must use the exact same method signatures as are defined in the interface 10/9/2011 22 [email protected]
- 23. INTERFACE CONSTANTS interfaces can have constants Interface constants works exactly like class constants except they cannot be overridden by a class/interface that inherits it 10/9/2011 23 [email protected]
- 24. EXAMPLE: INTERFACES // Declare the interface 'iTemplate' interface iTemplate { public function setVariable($name, $var); public function getHtml($template); } // Implement the interface // This will work class Template implements iTemplate { private $vars = array(); public function setVariable($name, $var) { $this->vars[$name] = $var; } public function getHtml($template) { foreach($this->vars as $name => $value) { $template = str_replace('{' . $name . '}', $value, $template); } return $template; } } 10/9/2011 24 [email protected]
- 25. TRAITS Traits is a mechanism for code reuse in single inheritance languages such as PHP enabling a developer to reuse sets of methods freely in several independent classes living in different class hierarchies trait ezcReflectionReturnInfo { function getReturnType() { /*1*/ } function getReturnDescription() { /*2*/ } } class ezcReflectionMethod extends ReflectionMethod { use ezcReflectionReturnInfo; /* ... */ } class ezcReflectionFunction extends ReflectionFunction { use ezcReflectionReturnInfo; /* ... */ } 10/9/2011 25 [email protected]
- 26. PRECEDENCE AND TRAITS An inherited member from a base class is overridden by a member inserted by a Trait The precedence order is that members from the current class override Trait methods which in return override inherited methods Traits override base methods but current methods override traits 10/9/2011 26 [email protected]
- 27. OVERLOADING Overloading in PHP provides means to dynamically "create" properties and methods These dynamic entities are processed via magic methods one can establish in a class for various action types The overloading methods are invoked when interacting with properties or methods that have not been declared or are not visible in the current scope All overloading methods must be defined as public None of the arguments of these magic methods can be passed by reference 10/9/2011 27 [email protected]
- 28. METHOD OVERLOADING 5.3.0 Added __callStatic(). Added warning to enforce public visibility and non-static declaration 5.1.0 Added __isset() and __unset() 10/9/2011 28 [email protected]
- 29. PROPERTY OVERLOADING void __set ( string $name , mixed $value ) mixed __get ( string $name ) bool __isset ( string $name ) void __unset ( string $name ) __set() is run when writing data to inaccessible properties. __get() is utilized for reading data from inaccessible properties. __isset() is triggered by calling isset() or empty() on inaccessible properties. __unset() is invoked when unset() is used on inaccessible properties. 10/9/2011 29 [email protected]
- 30. PROPERTY OVERLOADING Property overloading only works in object context 10/9/2011 30 [email protected]
- 31. METHOD OVERLOADING Method overloading mixed __call ( string $name , array $arguments ) mixed __callStatic ( string $name , array $arguments ) __call() is triggered when invoking inaccessible methods in an object context __callStatic() is triggered when invoking inaccessible methods in a static context 10/9/2011 31 [email protected]
- 32. ACHIEVING JAVA LIKE OVERLOADING If you want to overload a function like in Java, don’t specify any arguments and use the func_num_args and func_get_args function to get the number of arguments or the arguments themselves that were passed to that function: function test() { $args = function_get_args(); swtich (count($args)) { case 1: // one argument passed break; case 2: // two arguments passed break; default: // illegal numer of arguments break; } } http://stackoverflow.com/questions/1512295/what-is-php-function- overloading-for 10/9/2011 32 [email protected]
- 33. IS PHP OVERLOADING USEFUL When can you use PHP overloading Check: http://stackoverflow.com/questions/1512295/what-is-php- function-overloading-for 10/9/2011 33 [email protected]
- 34. OBJECT ITERATION PHP 5 provides a way for objects to be defined so it is possible to iterate through a list of items foreach statement. By default, all visible properties will be used for the iteration. you can implement one of PHP 5's internal interface named Iterator. This allows the object to decide what and how the object will be iterated. Interface methods to override: rewind(), current(), key() , next() , valid() 10/9/2011 34 [email protected]
- 35. SPL ITERATORS SPL Iterators http://ca.php.net/manual/en/spl.iterators.php AppendIterator ArrayIterator CachingIterator CallbackFilterIterator DirectoryIterator EmptyIterator FilesystemIterator FilterIterator GlobIterator InfiniteIterator IteratorIterator LimitIterator 10/9/2011 35 [email protected]
- 36. SPL ITERATORS MultipleIterator NoRewindIterator ParentIterator RecursiveArrayIterator RecursiveCachingIterator RecursiveCallbackFilterIterator RecursiveDirectoryIterator RecursiveFilterIterator RecursiveIteratorIterator RecursiveRegexIterator RecursiveTreeIterator RegexIterator SimpleXMLIterator 10/9/2011 36 [email protected]
- 37. PHP PATTERNS show a flexible solution to common programming problems. Factory allows for the instantiation of objects at runtime class Example { // The parameterized factory method public static function factory($type) { if (include_once 'Drivers/' . $type . '.php') { $classname = 'Driver_' . $type; return new $classname; } else { throw new Exception('Driver not found'); } } } // Load a MySQL Driver $mysql = Example::factory('MySQL'); // Load an SQLite Driver $sqlite = Example::factory('SQLite'); 10/9/2011 37 [email protected]
- 38. PHP PATTERNS Singleton The Singleton ensures that there can be only one instance of a Class and provides a global access point to that instance often implemented in Database Classes Loggers Front Controllers or Request and Response objects 10/9/2011 38 [email protected]
- 39. SINGLETON EXAMPLE class Example { private static $instance; private $count = 0; private function __construct() { } public static function singleton() { if (!isset(self::$instance)) { echo 'Creating new instance.'; $className = __CLASS__; self::$instance = new $className; } return self::$instance; } 10/9/2011 39 [email protected]
- 40. USE OF SINGLETON $singleton = Example::singleton(); // prints "Creatin g new instance." echo $singleton->increment(); // 0 echo $singleton->increment(); // 1 $singleton = Example::singleton(); // reuses existing instance now echo $singleton->increment(); // 2 echo $singleton->increment(); // 3 // all of these will raise a Fatal Error $singleton2 = new Example; $singleton3 = clone $singleton; $singleton4 = unserialize(serialize($singleton)); 10/9/2011 40 [email protected]
- 41. MAGIC METHODS __construct(), __destruct(), __call(), __callStatic(), __get(), __set(), __isset(), __unset(), __sleep(), __wakeup(), __toString(), __invoke(), __set_state() and __clone() 10/9/2011 41 [email protected]
- 42. MAGIC METHODS serialize() checks if your class has a function with the magic name __sleep(). unserialize() checks for the presence of a function with the magic name __wakeup() 10/9/2011 42 [email protected]
- 43. FINAL KEYWORD Can be used before A class name A method name Properties cannot be declared final, only classes and methods may be declared as final. prevents child classes from overriding a method by prefixing the definition with final if the class itself is being defined final then it cannot be extended 10/9/2011 43 [email protected]
- 44. OBJECT CLONING To create a copy of an existing object 10/9/2011 44 [email protected]
- 45. COMPARING OBJECTS Using == Two object instances are equal if they have the same attributes and values, and are instances of the same class. Using === object variables are identical if and only if they refer to the same instance of the same class. 10/9/2011 45 [email protected]
- 46. TYPE HINTING Functions are now able to force parameters to be objects or arrays // An example class class MyClass { /** * A test function * * First parameter must be an object of type OtherClass */ public function test(OtherClass $otherclass) { echo $otherclass->var; } /** * Another test function * * First parameter must be an array */ public function test_array(array $input_array) { print_r($input_array); } } 10/9/2011 46 [email protected]
- 47. LATE STATIC BINDINGS To address the limitations of self:: Class A { public static function who() { echo __CLASS__; } public static function test() { static::who(); // Here comes Late Static Bindings (instead of self) } } class B extends A { public static function who() { echo __CLASS__; } } B::test(); 10/9/2011 47 [email protected]
- 48. OBJECT SERIALIZATION serialize() returns a string containing a byte-stream representation of any value that can be stored in PHP spl_autoload_register() function 10/9/2011 48 [email protected]
- 49. OTHER OOP FEATURES namespaces http://ca.php.net/manual/en/language.namespaces.php Predefined Interfaces http://ca.php.net/manual/en/reserved.interfaces.php Predefined Exceptions http://ca.php.net/manual/en/reserved.exceptions.php 10/9/2011 49 [email protected]
- 50. OOP CHANGELOG http://ca.php.net/manual/en/language.oop5.changelog.php 5.4.0 Changed: If an abstract class defines a signature for the constructor it will now be enforced. 5.3.3 Changed: Methods with the same name as the last element of a namespaced class name will no longer be treated as constructor. This change doesn't affect non-namespaced classes. 5.3.0 Changed: Classes that implement interfaces with methods that have default values in the prototype are no longer required to match the interface's default value. 5.3.0 Changed: It's now possible to reference the class using a variable (e.g., echo $classname::constant;). The variable's value can not be a keyword (e.g., self, parent or static). 5.3.0 Changed: An E_WARNING level error is issued if the magic overloading methods are declared static. It also enforces the public visibility requirement. 5.3.0 Changed: Prior to 5.3.0, exceptions thrown in the __autoload function could not be caught in the catch block, and would result in a fatal error. Exceptions now thrown in the __autoload function can be caught in the catch block, with one proviso. If throwing a custom exception, then the custom exception class must be available. The __autoload function may be used recursively to autoload the custom exception class. 5.3.0 Added: The __callStatic method. 10/9/2011 50 [email protected]
- 51. OOP CHANGELOG 5.3.0 Added: heredoc and nowdoc support for class const and property definitions. Note: heredoc values must follow the same rules as double- quoted strings, (e.g., no variables within). 5.3.0 Added: Late Static Bindings. 5.3.0 Added: The __invoke method. 5.2.0 Changed: The __toString method was only called when it was directly combined with echo() or print(). But now, it is called in any string context (e.g. in printf() with %s modifier) but not in other types contexts (e.g. with %d modifier). Since PHP 5.2.0, converting objects without a __toString method to string emits a E_RECOVERABLE_ERROR level error. 5.1.3 Changed: In previous versions of PHP 5, the use of var was considered deprecated and would issue an E_STRICT level error. It's no longer deprecated, therefore does not emit the error. 5.1.0 Changed: The __set_state static method is now called for classes exported by var_export(). 5.1.0 Added: The __isset and __unset methods. 10/9/2011 51 [email protected]