Editing PHP

==Comments==
 // single line
 /*
    multiple line
 */

==Functions==
* function arguments:
** bool
** int
** float
** string
** array
** callable
** self
** iterable
** object
** class
** interface

==OO==
* namespace?
* interface?
* self?
* method
* $this?
* use?
* annotations?
* visibility:
** private: only in this class
** protected: only in derived classes
** public: everywhere
* ctor
 function __construct() {
   parent::__construct(); // has to be called explicitly
   ...
 }
There can only be one ctor which can have function parameters.
* dtor
 function __destruct() {
   parent::__destruct(); // has to be called explicitly
 }
* inheritance
 class B extends A
 {
    public function __construct()
    {
      parent::__construct();
* trait: a trait is similar to a class, but only intended to group functionality in a fine-grained and consistent way. It is not possible to instantiate a Trait on its own. It is an addition to traditional inheritance and enables horizontal composition of behavior; that is, the application of class members without requiring inheritance.

==PHP Standard Recommendation (PSR)==
* [https://www.php-fig.org/psr/psr-1/ PSR-1]
** each sub-word should be capitalised in both instances, with classes having an initial upper-case letter (StudlyCaps) and methods an initial lower-case letter (camelCase)
** Class constants MUST be declared in all upper case with underscore separators
* [ PSR-3] is the logger interface
* [https://www.php-fig.org/psr/psr-2/ PSR-2]
* [https://www.php-fig.org/psr/psr-4/ PSR-4]

==PDO==
PHP Data Objects ('''PDO''') is a Database Access Abstraction Layer.

==Exceptions==
The base '''Exception''' class provided in PHP 5 can be extended.

==PHPUnit==
PHPUnit provides a simple framework for creating a test suite to automate testing of functions and classes. 

===Installation===

==XDebug==
* documentation see [https://xdebug.org/docs/ here]
* activate in php.ini an restart web server
* XDebug will not automatically start a debugging session, but it needs to be activated in one of three ways
** before starting a PHP script from command line by set the environment variable XDEBUG_CONFIG
** calling a PHP script from a web browser by using setting the GET parameter XDEBUG_SESSION_START, by setting it as a POST parameter of through a cookie named XDEBUG_SESSION
** last can be set by using a browser extension for XDebug

==Resources==
* http://php.net/manual/en/
* [http://www.phpdoc.de/ PHPDoc]
* [https://docs.phpdoc.org PHPDocumentor]