How to Dynamically Invoke a Class Method in PHP?

In PHP there are various ways in which you can dynamically invoke a static or non-static method. To learn about them, let's suppose we have the following variables; one referencing a class name, another an instantiated object, and a static and non-static method name:

$className = ClassName::class;
$obj = new ClassName();

$nonStaticMethod = 'nonStaticMethod';
$staticMethod = 'staticMethod';

To dynamically invoke the methods you can do any of the following:

Using the Variable Function Syntax

You can use the variable function syntax with class methods in the following ways:

Dynamically Invoking a Non-Static Method:

You can use the method name variable directly on the object instance variable similar to how you normally would without a variable method name. For example:

// PHP 5.5+
$obj->$nonStaticMethod();

// or
$obj->{$nonStaticMethod}();

Dynamically Invoking a Static Method:

If you have both, the class name (or the object instance) and the method name as a variable, then you could dynamically invoke the static method in the following way:

// PHP 5.5+
$className::$staticMethod();

// PHP 5.5+
$obj::$staticMethod();

If only the class name or object instance exists as a variable, you could directly write the method name in a single, combined string (which you could then invoke as a callable) like so:

// PHP 7+
$callable = "{$className}::staticMethod";
$callable();

You could also inline this callable string in the following way:

("{$className}::staticMethod")();

Since the callable string syntax returns a callable, you could also pass it as the first argument to either call_user_func() or call_user_func_array() function, for example, like so:

$callable = $obj::$staticMethod();

// or
// $callable = $className::$staticMethod();

call_user_func($callable, $arg1, $arg2, ...);

call_user_func_array($callable, [$arg1, $arg2, ...]);

Using the Callable Array Syntax

You can use the callable array syntax, where you specify the object instance or class name at index 0 and the method name at index 1 (regardless of whether it's a static method or a non-static one). For example:

// PHP 5.5+
$callable = [$obj, $nonStaticMethod];
$callable();

// PHP 5.5+
$callable = [$obj, $staticMethod];
$callable();

// PHP 5.5+
$callable = [$className, $staticMethod];
$callable();

You could also inline the whole call in the following way:

([$obj, $nonStaticMethod])();
([$obj, $staticMethod])();
// ...

Since the callable array syntax returns a callable, you could also pass it as the first argument to either call_user_func() or call_user_func_array() function, for example, like so:

$callable = [$obj, $nonStaticMethod];

call_user_func($callable, $arg1, $arg2, ...);

call_user_func_array($callable, [$arg1, $arg2, ...]);

It works the same way for both static and non-static methods.