PHP, Structures and Functions, ArrayObjects

Magical Constants

computer apg

To allow to determine the line number, the full path and filename of the file with symlinks resolved, the directory of the file.

If used inside an include, the directory of the included file is returned, the function name, the class name, the trait name, the class method and the namespace.

PHP provides a large number of predefined constants to any script which it runs.

Many of these constants, however, are created by various extensions, and will only be present when those extensions are available, either via dynamic loading or because they have been compiled in.

These special constants are case-insensitive.

All these Magical Constants are resolved at compile time, unlike Regular Constants, which are resolved at runtime.

MAGICAL CONSTANTS
NAME	MEANING
__LINE__	The current line number of the file.
__FILE__	The full path and filename of the file with symlinks resolved. If used inside an include, the name of the included file is returned.
__DIR__	The directory of the file. If used inside an include, the directory of the included file is returned. This is equivalent to dirname(__FILE__). This directory name does not have a trailing slash unless it is the root directory.
__FUNCTION__	The function name, or {closure} for anonymous functions.
__CLASS__	The class name. The class name includes the namespace it was declared in (e.g. Foo\Bar). Note that as of PHP 5.4 __CLASS__ works also in traits. When used in a trait method, __CLASS__ is the name of the class the trait is used in.
__TRAIT__	The trait name. The trait name includes the namespace it was declared in (e.g. Foo\Bar).
__METHOD__	The class method name.
__NAMESPACE__	The name of the current namespace.
ClassName::class	The fully qualified class name.
ed48

EXERCISE


<?php

class AIterator implements Iterator {
    private $position = 0;
    private $array = [ 'South America', 'Central America', 'North America' ];  

    public function __construct() {
        $this->position = 0;
        writemsg('<br>');
    }

    public function rewind() {
        writemsg('REWIND TO INITIAL KEY<br>');
        var_dump(__METHOD__);
        writemsg('<br>');
        $this->position = 0;
        writemsg('<br>');
    }

    public function current() {
        writemsg('<br>CURRENT KEY<br>');
        var_dump(__METHOD__);
        writemsg('<br>');
        return $this->array[$this->position];
        writemsg('<br>');
    }

    public function key() {
        var_dump(__METHOD__);
        writemsg('<br>');
        return $this->position;
        writemsg('<br>');
    }

    public function next() {
        writemsg('NEXT KEY<br>');
        var_dump(__METHOD__);
        writemsg('<br>');
        ++$this->position;
        writemsg('<br>');
    }

    public function valid() {
        var_dump(__METHOD__);
        writemsg('<br>');
        return isset($this->array[$this->position]);
        writemsg('<br>');
    }
}

  function writemsg($msg) {
    echo $msg;
  }

$iterator = new AIterator;

foreach($iterator as $key => $value) {
    writemsg('<br>');
    var_dump($key, $value);
    writemsg('<br>');
}

?>

RESULT

REWIND TO INITIAL KEY
string(18) "AIterator::rewind"

string(17) "AIterator::valid"

CURRENT KEY
string(19) "AIterator::current"
string(15) "AIterator::key"

int(0) string(13) "South America"

NEXT KEY
string(16) "AIterator::next"

string(17) "AIterator::valid"

CURRENT KEY
string(19) "AIterator::current"
string(15) "AIterator::key"

int(1) string(15) "Central America"

NEXT KEY
string(16) "AIterator::next"

string(17) "AIterator::valid"

CURRENT KEY
string(19) "AIterator::current"

string(15) "AIterator::key"

int(2) string(13) "North America"

NEXT KEY
string(16) "AIterator::next"

string(17) "AIterator::valid"

EXERCISE


<?php

class Country {
    private $country;
    private $president;
    function __construct($president_in, $country_in) {
      $this->country = $country_in;
      $this->president  = $president_in;
    }
    function getCcontry() {return $this->country;}
    function getTpresident() {return $this->president;}
    function getCcontryAndTpresident() {
      return $this->getTpresident() . ' by ' . $this->getCcontry();
    }
}

class CountryList {
    private $countrys = array();
    private $countryCount = 0;
    public function __construct() {
    }
    public function getCountryCount() {
      return $this->countryCount;
    }
    private function setCountryCount($newCount) {
      $this->countryCount = $newCount;
    }
    public function getCountry($countryNumberToGet) {
      if ( (is_numeric($countryNumberToGet)) && 
           ($countryNumberToGet <= $this->getCountryCount())) {
           return $this->countrys[$countryNumberToGet];
         } else {
           return NULL;
         }
    }
    public function addCountry(Country $country_in) {
      $this->setCountryCount($this->getCountryCount() + 1);
      $this->countrys[$this->getCountryCount()] = $country_in;
      return $this->getCountryCount();
    }
    public function removeCountry(Country $country_in) {
      $counter = 0;
      while (++$counter <= $this->getCountryCount()) {
        if ($country_in->getCcontryAndTpresident() == 
          $this->countrys[$counter]->getCcontryAndTpresident())
          {
            for ($x = $counter; $x < $this->getCountryCount(); $x++) {
              $this->countrys[$x] = $this->countrys[$x + 1];
          }
          $this->setCountryCount($this->getCountryCount() - 1);
        }
      }
      return $this->getCountryCount();
    }
}

class CountryListIterator {
    protected $countryList;
    protected $currentCountry = 0;

    public function __construct(CountryList $countryList_in) {
      $this->countryList = $countryList_in;
    }
    public function getCurrentCountry() {
      if (($this->currentCountry > 0) && 
          ($this->countryList->getCountryCount() >= $this->currentCountry)) {
        return $this->countryList->getCountry($this->currentCountry);
      }
    }
    public function getNextCountry() {
      if ($this->hasNextCountry()) {
        return $this->countryList->getCountry(++$this->currentCountry);
      } else {
        return NULL;
      }
    }
    public function hasNextCountry() {
      if ($this->countryList->getCountryCount() > $this->currentCountry) {
        return TRUE;
      } else {
        return FALSE;
      }
    }
}

class CountryListReverseIterator extends CountryListIterator {
    public function __construct(CountryList $countryList_in) {
      $this->countryList = $countryList_in;
      $this->currentCountry = $this->countryList->getCountryCount() + 1;
    }
    public function getNextCountry() {
      if ($this->hasNextCountry()) {
        return $this->countryList->getCountry(--$this->currentCountry);
      } else {
        return NULL;
      }
    }
    public function hasNextCountry() {
      if (1 < $this->currentCountry) {
        return TRUE;
      } else {
        return FALSE;
      }
    }
}


  writeln('BEGIN TESTING ITERATOR PATTERN');
  writeln('');
 
  $firstCountry = new Country('Spain', 'Pedro Sánchez');
  $secondCountry = new Country('Germany', 'Frank-Walter Steinmeier');
  $thirdCountry = new Country('Portugal', 'Marcelo Rebelo de Souza');

  $countrys = new CountryList();
  $countrys->addCountry($firstCountry);
  $countrys->addCountry($secondCountry);
  $countrys->addCountry($thirdCountry);
 
  writeln('Testing the Iterator');
 
  $countrysIterator = new CountryListIterator($countrys);

  while ($countrysIterator->hasNextCountry()) {
    $country = $countrysIterator->getNextCountry();
    writeln('getting next country with iterator:');
    writeln($country->getCcontryAndTpresident());
    writeln('');
  }
 
  $country = $countrysIterator->getCurrentCountry();
  writeln('getting current country with iterator:');
  writeln($country->getCcontryAndTpresident());
  writeln('');  

  writeln('Testing the Reverse Iterator');

  $countrysReverseIterator = new CountryListReverseIterator($countrys);

  while ($countrysReverseIterator->hasNextCountry()) {
    $country = $countrysReverseIterator->getNextCountry();
    writeln('getting next country with reverse iterator:');
    writeln($country->getCcontryAndTpresident());
    writeln('');
  }
 
  $country = $countrysReverseIterator->getCurrentCountry();
  writeln('getting current country with reverse iterator:');
  writeln($country->getCcontryAndTpresident());
  writeln('');

  writeln('END TESTING ITERATOR PATTERN');
 
  function writeln($line_in) {
    echo $line_in . "<br>";
  }

?>

RESULT

BEGIN TESTING ITERATOR PATTERN

Testing the Iterator
getting next country with iterator:
Spain by Pedro Sánchez

getting next country with iterator:
Germany by Frank-Walter Steinmeier

getting next country with iterator:
Portugal by Marcelo Rebelo de Souza

getting current country with iterator:
Portugal by Marcelo Rebelo de Souza

Testing the Reverse Iterator

getting next country with reverse iterator:
Portugal by Marcelo Rebelo de Souza

getting next country with reverse iterator:
Germany by Frank-Walter Steinmeier

getting next country with reverse iterator:
Spain by Pedro Sánchez

getting current country with reverse iterator:
Spain by Pedro Sánchez

END TESTING ITERATOR PATTERN