Tutorial by Examples

Introduction Interfaces are definitions of the public APIs classes must implement to satisfy the interface. They work as "contracts", specifying what a set of subclasses does, but not how they do it. Interface definition is much alike class definition, changing the keyword class to inter...

Class constants provide a mechanism for holding fixed values in a program. That is, they provide a way of giving a name (and associated compile-time checking) to a value like 3.14 or "Apple". Class constants can only be defined with the const keyword - the define function cannot be used in...

In PHP 5.3+ and above you can utilize late static binding to control which class a static property or method is called from. It was added to overcome the problem inherent with the self:: scope resolutor. Take the following code class Horse { public static function whatToSay() { echo ...

An abstract class is a class that cannot be instantiated. Abstract classes can define abstract methods, which are methods without any body, only a definition: abstract class MyAbstractClass { abstract public function doSomething($a, $b); } Abstract classes should be extended by a child cla...

Technically, autoloading works by executing a callback when a PHP class is required but not found. Such callbacks usually attempt to load these classes. Generally, autoloading can be understood as the attempt to load PHP files (especially PHP class files, where a PHP source file is dedicated for a ...

Dynamic binding, also referred as method overriding is an example of run time polymorphism that occurs when multiple classes contain different implementations of the same method, but the object that the method will be called on is unknown until run time. This is useful if a certain condition dicta...

There are three visibility types that you can apply to methods (class/object functions) and properties (class/object variables) within a class, which provide access control for the method or property to which they are applied. You can read extensively about these in the PHP Documentation for OOP Vi...

A common pitfall of child classes is that, if your parent and child both contain a constructor(__construct()) method, only the child class constructor will run. There may be occasions where you need to run the parent __construct() method from it's child. If you need to do that, then you will need to...

Def: Final Keyword 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 Final Method class BaseClass { public function test() { echo "BaseClass::test() called\n"; } ...

Use $this to refer to the current object. Use self to refer to the current class. In other words, use $this->member for non-static members, use self::$member for static members. In the example below, sayHello() and sayGoodbye() are using self and $this difference can be observed here. cl...

Nobody wants to require or include every time a class or inheritance is used. Because it can be painful and is easy to forget, PHP is offering so called autoloading. If you are already using Composer, read about autoloading using Composer. What exactly is autoloading? The name basically says it al...

Anonymous classes were introduced into PHP 7 to enable for quick one-off objects to be easily created. They can take constructor arguments, extend other classes, implement interfaces, and use traits just like normal classes can. In its most basic form, an anonymous class looks like the following: ...

An object in PHP contains variables and functions. Objects typically belong to a class, which defines the variables and functions that all objects of this class will contain. The syntax to define a class is: class Shape { public $sides = 0; public function description() { ...