Create and use anonymous object in PHP

Question

Say I have a simple class and I create it and call a function on it like this:

class tst
{
  private $s = "";

  public function __construct( $s )
  {
    $this->s = $s;
  }

  public function show()
  {
    return $this->s;
  }
}

$t = new tst( "hello world" );
echo "showing " . $t->show() . "\n";

Is there any syntax or workaround that will allow me to instantiate an instance of tst and call the show() function without assigning the object to a variable? I want to do something like:

echo new tst( "again" )->show();

I don't want to declare my functions as static as I want to use them in both of the above examples.

What advantage does tst::create(x)->show() over just using x?!? Or f(x) if there's actually some work (validation, normalization, conversion) ones in the constructor? — user395760
– user395760, Commented Apr 4, 2011 at 15:40
@delnan: Your question is equivalent to asking "why use classes in programming?". A more relevant question (but one which I feel is adequately answered by the OP) is "why not make the methods static?". — Jon
– Jon, Commented Apr 4, 2011 at 15:48
@Jon: Rest assured that I know, understand and appreciate OOP. But wrapping something in this class, which does nothing, and then retrieving the wrapped value instantly, seems pretty useless. The equivalent of (function (x) { return x; })(x) in JS, if you will. And even if the constructor did something useful with that value, there's no need to wrap the result in an extra object. — user395760
– user395760, Commented Apr 4, 2011 at 15:50
@delnan: I see, and of course I agree with you. But I believe the OP is just giving us an example here; that's probably not what the real class does. — Jon
– Jon, Commented Apr 4, 2011 at 15:59
@delnan - I take your point, the example does nothing useful. It was the simplest code to illustrate what I wanted to do and my real code does not have simple show() functions but others that actually manipulate the variable passed in the constructor — Steve Claridge
– Steve Claridge, Commented Apr 4, 2011 at 16:00

Galen · Accepted Answer · 2011-04-04 15:43:21Z

3

You can't do what you want exactly, but there are workarounds without making things static.

You can make a function that returns the new object

function tst( $s ) {
    return new tst( $s );
}

echo tst( "again" )->show();

answered Apr 4, 2011 at 15:43

Galen

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Jon · Accepted Answer · 2011-04-04 15:35:27Z

3

To answer your question:

public static function create( $s )
{
    return new tst($s);
}

public function show()
{
    return $this->s;
}

The above will allow you to do tst::create("again")->show(). You can rename create as you like.

answered Apr 4, 2011 at 15:35

Jon

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2 Comments

Steve Claridge Over a year ago

Thanks for the answer. I accepted Galen's as it results in slightly cleaner syntax.

Jon Over a year ago

@SteveClaridge: Regardless of the accept, I feel that having an extra free function (with a parameter list that needs to be kept in sync with the class constructor) in order to save 5 keystrokes is not the best approach. But it's your code, your decision.

romaninsh · Accepted Answer · 2011-04-04 16:20:43Z

Agile Toolkit uses this approach everywhere. It uses add() method wrapper which is defined for global object ancestor. Here is some real-life code:

$page
    ->add('CRUD')
    ->setModel('User')
    ->setMasterField('admin',false);

This code creates 'CRUD' view, puts it on the page, creates and links with Model_User class instance which receives additional condition and default value for boolean 'admin' field.

It will display a CRUD control on the page with add/edit/delete allowing to edit all users except admins.

Here is code to describe concept:

class AbstractObject {
    public $owner;
    function add($class){
        $c=new $class;
        $c->owner=$this;
        return $c;
    }
}

class Form extends AbstractObject {
    function dosomething(){
        return $this;
    }
}
class OtherForm extends Form {}

$object->add('Form')->dosomething()->owner
       ->add('OtherForm');  // etc

I think it's awesome and very practical approach.

p.s. I have to note new syntax for exceptions:

throw $this->exception('Something went bad');

using $this links exception to the object, which is at fault, which also can set default class for exception.

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