PHP syntax: constructing a class from a member variable

Question

I am trying to make a class from a member variable like this:

<?
class A{
    private $to_construct = 'B'; 
    function make_class(){
        // code to make class goes here
    }

}

class B{
    function __construct(){
        echo 'class constructed';
    }
}

$myA = new A();
$myA->make_class();
?>

I tried using:

 $myClass = new $this->to_construct();

and

$myClass = new {$this->to_construct}();

but neither worked. I ended up having to do this:

$constructor = $this->to_construct;
$myClass = new $constructor();

It seems like there should be a way to do this without storing the class name in a local variable. Am I missing something?

jkeys · Accepted Answer · 2009-07-18 18:10:30Z

3

Have you tried this?

 $myClass = new $this->to_construct;

answered Jul 18, 2009 at 18:10

jkeys

3,98511 gold badges41 silver badges63 bronze badges

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

2 Comments

Craig Over a year ago

Thanks, I was thinking I needed to put the parenthesis to show it was a function. Is there still a way to do this without having to store the local class name if you need to pass parameters to the constructor?

jkeys Over a year ago

It's not a function, though. I'm not sure how you would do what you need in PHP, either.

Taryn · Accepted Answer · 2013-07-19 15:00:28Z

2

Are you using PHP 4 or something? On 5.2.9 $myClass = new $this->to_construct(); works perfectly.

In the end it's what you have to live with, with PHP. PHP syntax and semantics are VERY inconsistent. For example, an array access to the result of a call is a syntax error:

function foo() {
  return array("foo","bar");
}
echo $foo()[0];

Any other language could do that but PHP can't. Sometimes you simply need to store values into local variables.

Same is true for func_get_args() in older versions of PHP. If you wanted to pass it to a function, you needed to store it in a local var first.

edited Jul 19, 2013 at 15:00

Taryn

249k57 gold badges375 silver badges409 bronze badges

answered Jul 18, 2009 at 18:50

back2dos

15.6k36 silver badges52 bronze badges

Comments

damko · Accepted Answer · 2009-07-18 18:55:40Z

0

If I read well between the lines you are trying to do something like this. Right?

class createObject{
    function __construct($class){
        $this->$class=new $class;
    }

}

class B{
    function __construct(){
        echo 'class B constructed<br>';
    }
    function sayHi(){
        echo 'Hi I am class: '.get_class();
    }
}

class C{
    function __construct(){
        echo 'class C constructed<br>';
    }
    function sayHi(){
        echo 'Hi I am class: '.get_class();
    }
}
$wantedClass='B';
$finalObject = new createObject($wantedClass);
$finalObject->$wantedClass->sayHi();

--
Dam

answered Jul 18, 2009 at 18:55

damko

2911 silver badge13 bronze badges

Collectives™ on Stack Overflow

PHP syntax: constructing a class from a member variable

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related