I want to learn about PHP Anotations - php

Question

What is PHP Anotations and where can I learn more about it? I need simple example to understand it. I have googled around alot. Somehow i reached this point:
Example Code:
<?php
class AddressShipment{
/* Attributes of AddressShipment */
/**
* private TypePlaceShipment type
* #ORM\Id #ORM\Column #ORM\GeneratedValue
* #dummy
* #var long
*/
private $type;
/**
* private boolean lift
* #ORM\Column(type="boolean")
* #Assert\NotEmpty
* #var boolean
*/
private $lift;
/**
* private String comment
* #ORM\Column(type="string")
* #Assert\NotEmpty
* #var string
*/
private $comment;
?>
Can someone explain this a bit ? What are PHP Anotations? How can we use it ? What is the purpose of using it ?

Answer 1

It is basically for documentation generation.
Also IDEs which support php look up the annotations and give you information on what the function does, what it returns, what parameter it takes.
So if you make a php library, another person can read the annotations easily to know what it does without having to dig through your code and his IDE will recognize those annotations
here is an example of netbeans using this annotation from a function somewhere
You can learn by visiting this link:
http://manual.phpdoc.org/HTMLSmartyConverter/PHP/phpDocumentor/tutorial_elements.pkg.html

Answer 2

Aside from providing documentation (e.g. http://www.phpdoc.org/ ) and providing hints for the IDE, some libraries use annotations to determine how to handle classes. One example is Doctrine which provides an Object Relational Mapper that can map objects to a database based on annotations (using its database abstraction layer).
In the given code fragment I recognize #ORM\Id, #ORM\Column and #ORM\GeneratedValue as some of the annotations that Doctrine uses. However, AddressShipment is not declared as an Entity with the appropriate annotation, so they're not correctly used for that purpose.
Zend Framework 2 utilizes Doctrine's annotation library to enable the creation of forms from annotations (including validations and filtering).
Under the hood Doctrine uses reflection to read these annotations. If you use annotation-dependent libraries in combination with certain PHP accelerators, then you need to take care to configure the accelerator not to discard the annotations when it caches the code.

Answer 3

(Take note before reading that in fact I know you are talking about how to use some php ORM framework documentation tags and where to find what they mean).
Annotations are just annotations in PHP world they are called "PHPDoc Tags" but unfortunately they are used for nothing more than some PHP IDE code autocompletion / intellisense / documentation generation.
PHPDoc by itself is a standard that raised from nowhere but opensource php documentation project many years ago and was positively received from php community and now even php reflection class supports them.
For example phpdoc tag #return specifies what will be php class method return type or php function return type.
#var specifies what is property type. PHPDoc has its own declaration rules. For example documentation must begin with /** and must and with */. You can find this standards on http://en.wikipedia.org/wiki/PHPDoc#Tags link.
In example below all tags with # symbol are legal and might be treated by some PHP IDE like Netbeans or Eclipse or even Sublime sometimes. But:
class planet
{
/**
* primary
* length 16
* #var string
*/
public $name;
/**
* type smallint
* #var integer
*/
public $order;
/**
* #var boolean
*/
public $water;
/**
* #var \galaxy\star
*/
public $star;
/**
* enum
* #var \galaxy\moon
*/
public $moons = array ();
But what is interesting in your question is that you also mentioned #ORM. This means you are using some ORM framework probably Doctrine with Symphony and you need to find what does these annotations mean for specific framework. This can be found easily in specific framework's documentation. They are so many that there is no clue to post them on here.
For example if you are planning to use Doctrine you can visit here http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/tutorials/getting-started.html
Or if you are using single file framework db.php which is database first style also and uses annotations as well you can visit here http://dbphp.net.