Question about Instantiating an obect

[eldan88]

Hey,

 

 I am new to OOP and just started using it. I wrote a simple question that calls a function that does an ehco. But for some reason everytime I call it it echo's the string twice. I'm not sure why. Below is the code i wrote.

 

<?php 


class Train {

var $train="e train";

function train() {
echo "I am in the " .$this->train;	
}

	
}


$train = new Train; 
$train->train();
?>

It echos out the following "I am in the e trainI am in the e train"

[requinix]

It's a holdover from the days of PHP 4: if you have a method with the same name as the class then it will consider that to be the constructor.

Rename the method or define a __construct() method (it can be empty, just matters that it exists).

[trq]

You could also put the class in a namespace which removes this backward compatibility.

<?php 


namespace Railway;


class Train {


  public $train = "e train";


  public function train() {

    echo "I am in the " .$this->train;	

  }	

}


$train = new Train; 

$train->train();

On a side note, use "public" in place of the older "var" keyword and you should also be explicit about your methods visibility IMO.

[ignace]

Here's an expanded example of your train in OO, for brevity most functions do not include code:

namespace Railway;


/* used as a flyweight */

class Passenger {

}


class PassengerFactory {

    const ECONOMY = 2;

    const BUSINESS = 1;


    private $economyPassenger; 

    private $businessPassenger;


    public function __construct() {

        $this->economyPassenger = new Passenger;

        $this->businessPassenger = new Passenger;

    }


    public function makePassenger($class = self::ECONOMY) {

        if ($class === self::BUSINESS) {

            return $this->getBusinessPassenger();

        } else {

            return $this->getEconomyPassenger();

        }

    }


    public function getEconomyPassenger() {

        return $this->enconomyPassenger;

    }


    public function getBusinessPassenger() {

        return $this->businessPassenger;

    }

}


class Station {}

class StationRoute {}


class Schedule {

    private $stationRoute;

    private $timeTable;

}


class Train {

    private $id;

    private $locomotive;

    private $wagons = array();

    private $stationRoute;

    private $schedule;


    public function __construct($id, Locomotive $locomotive, Array $wagons, StationRoute $route, Schedule $schedule) {}


    public function board(Passenger $passenger) {}


    public function attach(Wagon $wagon) {}

}


/** @internal */

class SplFixedArray {

    public function isAtCapacity() {

        return $this->count() === $this->getRealSize();

    }


    public function getRealSize() {

        return count(array_filter($this->toArray()));

    }

}


/** @internal */

class Locomotive extends SplFixedArray {

    public function __construct($maxWagons) {

        parent::__construct($maxWagons);

    }

}


/** @internal */

class Wagon extends SplFixedArray {

    public function __construct($capacity) {

        parent::__construct($capacity);

    }

}

[eldan88]

Oh okay i see. Thank you guys it makes a lot of sense.