How to check the user function existance?

[visweswaran2830]

Hi,
I created a web-page which contains functions like add(),sub(),div ide().. consider I am passing two value and functions name from first page. Then I received the values from first page and I want to check whether the function is exist or not. If exist means, the resultant value has to produce otherwise it has to display as "Not a valid function"..... How can I achieve this. Is any function to check availability.

[Dormilich]

function_exists ()

if you were to use objects (object methods), you can check against an interface or a class definition.

[visweswaran2830]

I cant get clearly. Could you explain with code snippet.

[Dormilich]

if (!function_exists("doSomething"))
{
    throw new Exception("You can’t do something!");
}

interface iTest
{
    public function doSomething();
}

class Abc
{
    private $someValue;

    public function __construct(iTest obj)
    {
        this->someValue = obj->doSomething();
    }
}

class Test implements iTest
{
    public function doSomething()
    {
        return "something";
    }
}

$y = new Abc(new stdClass); // throws an error
$y = new Abc(new Test); // doesn’t throw an error

[Markus]

For classes you might also use method_exists().