Check if method exists in the same class

Question

So, method_exists() requires an object to see if a method exists. But I want to know if a method exists from within the same class.

I have a method that process some info and can receive an action, that runs a method to further process that info. I want to check if the method exists before calling it. How can I achieve it?

Example:

class Foo{
    public function bar($info, $action = null){
        //Process Info
        $this->$action();
    }
}

Answer 1

You can do something like this:

class A{
    public function foo(){
        echo "foo";
    }

    public function bar(){
        if(method_exists($this, 'foo')){
            echo "method exists";
        }else{
            echo "method does not exist";
        }
    }
}

$obj = new A;
$obj->bar();

Answer 2

Using method_exists is correct. However if you want to conform to the "Interface Segregation Principle", you will create an interface to perform introspection against, like so:

class A
{
    public function doA()
    {
        if ($this instanceof X) {
            $this->doX();
        }

        // statement
    }
}

interface X
{
    public function doX();
}

class B extends A implements X
{
    public function doX()
    {
        // statement
    }
}

$a = new A();
$a->doA();
// Does A::doA() only

$b = new B();
$b->doA();
// Does B::doX(), then remainder of A::doA()

Answer 3

method_exists() accepts either a class name or object instance as a parameter. So you could check against $this

http://php.net/manual/en/function.method-exists.php

Parameters ¶

object An object instance or a class name

method_name The method name

Answer 4

The best way in my opinion is to use __call magic method.

public function __call($name, $arguments)
{
    throw new Exception("Method {$name} is not supported.");
}

Yes, you can use method_exists($this ...) but this is the internal PHP way.