How Can I Dynamically Create Class Instances in PHP Using a String?

Dynamic Instance Creation in PHP using a String

In PHP, there are situations where you might need to create an instance of a class using a string, instead of using a long switch statement to choose between multiple classes. For instance, let's say we have the following two classes:

class ClassOne {}
class ClassTwo {}

And we receive a string that can be either "One" or "Two". Rather than using a switch statement like:

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

We can dynamically create an instance using the following code:

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

The $class variable is dynamically constructed by concatenating the string 'Class' with the value of $str. Then, we use the new operator to create an instance of that class. This technique allows us to create instances of classes based on a string input dynamically.

The same approach can be used with namespaces by providing the fully qualified class name:

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

Additionally, PHP supports calling variable functions and methods dynamically using the following syntax:

$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();

However, it's important to note that creating variables dynamically is generally a bad practice and should be avoided whenever possible. Arrays are a better alternative in most cases.

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