Check if class has method in PHP

Question

Currently my code looks like that:

switch ($_POST['operation']) {
    case 'create':
        $db_manager->create();
        break;
    case 'retrieve':
        $db_manager->retrieve();
        break;
...
}

What I want to do is, to check if method called $_POST['operation'] exists: if yes then call it, else echo "error" Is it possible? How can I do this?

Brad Christie · Accepted Answer · 2012-04-23 20:32:51Z

47

You can use method_exists:

if (method_exists($db_manager, $_POST['operation'])){
  $db_manager->{$_POST['operation']}();
} else {
  echo 'error';
}

Though I strongly advise you don't go about programming this way...

answered Apr 23, 2012 at 20:32

Brad Christie

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9 Comments

Brad Christie Over a year ago

@epic_syntax: Because I could, with wget/cURL, spoof the POST variable and pry around for methods you don't necessarily want exposed. Also, you NEVER trust user input directly, you always want to sanitize it. basically, if you're using $_POST[...] anywhere else but the top of your file embedded in a check for safe-ness, you're doing it wrong and asking for trouble.

iblue Over a year ago

And I almost though, you'd recomend not to use PHP at all :)

zerkms Over a year ago

@epic_syntax: the easy way is to have whitelist of methods allowed to run

zerkms Over a year ago

@iblue: you just wanted to share that link and could find better place, didn't you?

Chubby Cows Over a year ago

@BradChristie There is any safer alternative for method_exists? Could you give a explanation about why you don't recommend using it?

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zerkms · Accepted Answer · 2012-04-23 20:32:55Z

13

You can use is_callable() or method_exists().

The difference between them is that the latter wouldn't work for the case, if __call() handles the method call.

answered Apr 23, 2012 at 20:32

zerkms

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Comments

Fad · Accepted Answer · 2012-04-23 20:33:01Z

6

Use method_exists()

method_exists($obj, $method_name);

answered Apr 23, 2012 at 20:33

Fad

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Comments

iblue · Accepted Answer · 2012-04-23 20:37:58Z

4

You can use method_exists(). But this is a really bad idea

If $_POST['operation'] is set to some magic function names (like __set()), your code will still explode. Better use an array of allowed function names.

answered Apr 23, 2012 at 20:37

iblue

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2 Comments

heron Over a year ago

I think, You mean something like this. $operations=array("retrieve", "create"); if (isset($_POST['operation']) && in_array($_POST['operation'], $operations)) { $db_manager->{$_POST['operation']}(); } Can I collect all available methods into an array automatically or only manually?

iblue Over a year ago

Letting users call arbitrary methods in an object is generally a bad idea (and its slow as hell). Make your own list, or even better use the switch statement from your question.

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