[php] Creating PHP class instance with a string

I have two classes, class ClassOne { } and class ClassTwo {}. I am getting a string which can be either "One" or "Two".

Instead of using a long switch statement such as:

switch ($str) {
    case "One":
        return new ClassOne();
    case "Two":
        return new ClassTwo();
}

Is there a way I can create an instance using a string, i.e. new Class("Class" . $str);?

Lets say ClassOne is defined as:

public class ClassOne
{
    protected $arg1;
    protected $arg2;

    //Contructor
    public function __construct($arg1, $arg2)
    {
        $this->arg1 = $arg1;
        $this->arg2 = $arg2;
    }

    public function echoArgOne
    {
        echo $this->arg1;
    }

}

Using PHP Reflection;

$str = "One";
$className = "Class".$str;
$class = new \ReflectionClass($className);

Create a new Instance:

$instance = $class->newInstanceArgs(["Banana", "Apple")]);

Call a method:

$instance->echoArgOne();
//prints "Banana"

Use a variable as a method:

$method = "echoArgOne";
$instance->$method();

//prints "Banana"

Using Reflection instead of just using the raw string to create an object gives you better control over your object and easier testability (PHPUnit relies heavily on Reflection)

have a look at example 3 from http://www.php.net/manual/en/language.oop5.basic.php

$className = 'Foo';
$instance = new $className(); // Foo()

You can simply use the following syntax to create a new class (this is handy if you're creating a factory):

$className = $whatever;
$object = new $className;

As an (exceptionally crude) example factory method:

public function &factory($className) {

    require_once($className . '.php');
    if(class_exists($className)) return new $className;

    die('Cannot create new "' . $className . '" class - includes not found or class unavailable.');
}