Using arrays in classes PHP

Question

I'm experimenting with classes and objects for the first time and I thought I'd make a template for a Box that can store things like Books. (Thinking in terms of real-world items)

<?php

function feetToInches($feet){
    $feet = $feet * 12;
    return $feet;
}



class Book{
    var $l = 6;
    var $w = 5;
    var $h = 1;
}

class Box{
    //This is a box. It has length, width, and height, and you can put things in it.
    var $length = 0;
    var $width = 0;
    var $height = 0;
    var $storedArray = array();

    function setDimensions($l, $w, $h){
        $this->length = feetToInches($l);
        $this->width = feetToInches($w);
        $this->height = feetToInches($h);
    }


    function storeThings($thing){
        $this->storedArray[] = $thing;
    }

    function getThings(){
       return $this->storedArray;
    }

}



$thatBook = new Book;
$BookBox = new Box;


$BookBox->setDimensions(6,5,1);


for($i = 0; $i < 5; $i++){
    $BookBox->storeThings($thatBook);
}


echo $BookBox->getThings() . "<br />";

/*
foreach($BookBox->getThings() as $item){
echo $item;
}
*/


var_dump($BookBox);

?>

So what I have is simple here, you have boxes of a dimension, and you throw books of a fixed dimension in them.

Putting things in it is no problem, but when I try to retrieve them, I either get errors or nothing happens. And when I try to specify a key for the array like

echo $BookBox->getThings()[2];

I get an error that it's not an array or something.

So can someone please point me in the right direction here?

And normally the class would be a separate file, but I'm just learning here.

Ayush · Accepted Answer · 2012-06-01 05:51:35Z

3

What version of PHP are you using.

Array dereferencing (referencing into a returned array) was only added in PHP 5.4.

If you're using a previous version, you'd have to do this:

$books = $BookBox->getThings();
echo $books[2];

Edit

Since you are pushing Books into a box, $books[2] returns you an instance of the Book object. Echo is used to output a string, hence the error.

You can either echo a particular property of the book, or print out all of the properties by doing:

print_r($books[2]);

edited Jun 1, 2012 at 5:51

answered Jun 1, 2012 at 5:41

Ayush

42.5k52 gold badges169 silver badges243 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

user1159454 Over a year ago

My version is 5.3.10. So you're saying if it was 5.4 my code would work?

Ayush Over a year ago

@user1159454: Yes, exactly. However, I wouldn't recommend using any PHP 5.4 only features as webhosts won't roll it out for some time.

user1159454 Over a year ago

Alright, I'm still getting an error. Catchable fatal error: Object of class Book could not be converted to string

flowfree · Accepted Answer · 2012-06-01 05:50:37Z

2

First, you cannot do echo since what you'll get is not a string but an object. Use print_r() or var_dump() instead.

Second, just like the other answers here, you should do this.

$books = $BookBox->getThings();
print_r($books[2]);

But I suggest you to make getThings() accept a variable for getting a specified array element:

function getThings($key = null) {
  if ($key) {
    return isset($this->storedArray[$key]) ? $this->storedArray[$key] : null;
  } else {
    return $this->storedArray;
  }
}

// Then you can do this
// print_r($BookBox->getThings(2));

answered Jun 1, 2012 at 5:50

flowfree

16.5k12 gold badges55 silver badges79 bronze badges

Comments

francisco.preller · Accepted Answer · 2012-06-01 05:41:48Z

0

What you are calling when you call $BookBox->getThings() is actually an object and not an array.

You might try something along the lines of:

$books = $BookBox->GetThings();
echo $books[2];

answered Jun 1, 2012 at 5:41

francisco.preller

6,6494 gold badges30 silver badges39 bronze badges

Collectives™ on Stack Overflow

Using arrays in classes PHP

3 Answers 3

3 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related