PHP function name on the fly

Question

Hi guys, I have a rather stupid PHP question :D! I would like to simplify the following statement:

function hello_input() {
    return 'Hello World';
}

$helper = 'hello';

$helper = $helper . '_input';

$data = $helperinput();

The specific part I want to simplify is the adding of the _input to the $helper so it calls the right function.

I thought of something like this but it doesn't work:

$data = $helper. 'input'();
or
$data = $helper. 'input' . ();

Any ideas?

Thanks, Max

Answer 1

Use call_user_func, e.g. $data = call_user_func($helper.'input');.

Answer 2

Although I recommend against it, you could do something like this:

$statement = $helper . '_input();';
$data = eval($statement);

The reason I recommend against it is that you'll be opening yourself up for code-injection attacks. But if it solves a problem and you can sanitize your inputs, have fun with it.

Edit:

I like @PiotrLegnica's solution better than mine. Much safer!

I was unaware of it. I guess you learn something new every day.

Answer 3

Get the whole function name into a string first.

$helper = 'hello';
$func = $helper . '_input';
$data = $func();

PHP calls this variable functions. See also variable variables.

Answer 4

$helper = 'hello_';
$data = $helper.'input';
call_user_func($data);

That should get you most of the way there. Good luck!

Docs here

Answer 5

Are you expecting to invoke code based on an input? You should never try to do that. That gives people the chance to execute arbitrary code. Even if you can't see quite how, it's still a potential method of attack.

What you probably want is a switch statement (or chained if statements) that match an input and dispatch the correct function.