CODEWITHSUNDEEP
php
Joel
Joel

Reputation: 6107

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);?

Upvotes: 288

Views: 275536

Answers (6)

DavSev
DavSev

Reputation: 1111

In case you have a namespace at the top of the file.

import the desired class at the top of the current file:

use \Foo\Bar\MyClass; 

// Assign the class namespace to a variable. 
$class = MyClass::class; 

// Create a new instance
$instance = new $class();

The ::class will return the entire namespace of the desired class

Upvotes: 1

Bob Fanger
Bob Fanger

Reputation: 29897

Yes, you can!

$str = 'One';
$class = 'Class'.$str;
$object = new $class();

When using namespaces, supply the fully qualified name:

$class = '\Foo\Bar\MyClass'; 
$instance = new $class();

You can also call variable functions & methods dynamically.

$func = 'my_function';
$parameters = ['param2', 'param2'];
$func(...$parameters); // calls my_function() with 2 parameters;

$method = 'doStuff';
$object = new MyClass();
$object->$method(); // calls the MyClass->doStuff() method. 
// or in one call
(new MyClass())->$method();

Also PHP can create variables with a string as well, but it's a really bad practice that should be avoided whenever possible. Consider to use arrays instead.

Upvotes: 600

DEV Tiago França
DEV Tiago França

Reputation: 1696

// Way #1
$className = "App\MyClass";
$instance = new $className();

// Way #2
$className = "App\MyClass";
$class = new \ReflectionClass($className);

// Create a new Instance without arguments:
$instance = $class->newInstance();

// Create a new Instance with arguments (need a contructor):
$instance = $class->newInstanceArgs(["Banana", "Apple"]);

Upvotes: 2

John Parker
John Parker

Reputation: 54415

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.');
}

Upvotes: 29

Remade
Remade

Reputation: 427

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)

Upvotes: 11

Freddie
Freddie

Reputation: 1707

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

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

Upvotes: 15

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