Calling different functions depending on the value of a given parameter

Question

The problem is actually quite easy, but somewhat difficult to explain, but I'll do my best.

Assume the following function and class:

somethingsomething.php

function do_something($a, $b, $whatToDo) {
    $value = someRandomClass::doThis();
    return $a + $b * $value;
}

someRandomClass.class.php

class someRandomClass {
    public static doThis() {
        return $this->valueThis;
    }
    public static doThat() {
        return $this->valueThat;
    }
    public static doSomethingElse() {
        return $this->valueSomethingElse;
    }
}

So, we have a function which does ... something. It gets 3 parameters:

$a = An integer

$b = Also an integer

$whatToDo. = A string, either this, that or somethingElse

As you can see, the calculation in do_something() requires a value which is received through one of the 3 functions in the class. But the function which is called should be defined by the value in $whatToDo. Of course, i could create an if- or switch-statement which would look like this:

function do_something($a, $b, $whatToDo) {
    if($whatToDo === "this") {
        $value = someRandomClass::doThis();
    } elseif ($whatToDo === "that") { 
        $value = someRandomClass::doThat();
    } elseif ($whatToDo === "somethingElse") {
        $value = someRandomClass::doSomethingElse();
    }
    return $a + $b * $value;
}

But this looks horrible and if I got more (the actual code can have up to 41 different "$whatToDo's") it's really difficult to read.

I wonder if there is a way to use a variable to "create" a function name and call that function, so something like:

function do_something($a, $b, $whatToDo) {
    $value = someRandomClass:: "do" . $whatToDo ."()";
    return $a + $b * $value;
}

so that if $whatToDo contains "this", it will call doThis().

Is that possible by any means necessary?

This is supposed to work like this: someRandomClass::{"do" . $whatToDo}(); but please try to search the net better next time. Src: http://stackoverflow.com/questions/1005857/how-to-call-php-function-from-string-stored-in-a-variable — dryman, Feb 11 '16 at 08:37
http://stackoverflow.com/questions/2108795/dynamic-static-method-call-in-php -> call_user_func('myClassName_' . $language . '::myFunctionName'); — Benjamin Poignant, Feb 11 '16 at 08:38
@dryman I searched for at least 20 minutes, but it's difficult to find something if you don't know how to describe what you're looking for. Google doesn't accept SO postsa search argument. Sorry. — Realitätsverlust, Feb 11 '16 at 08:39

score 4 · Accepted Answer · answered Feb 11 '16 at 08:38

4

You can made like this with a variable function:

 $fn = "do".$whatToDo."()"; // create a string with the function name
 $value = someRandomClass::$fn; // call it

More info:

http://php.net/manual/es/functions.variable-functions.php

answered Feb 11 '16 at 08:38

Marcos Pérez Gude

21,869
4
38
69

That's it, so simple, yet i was too stupid to find it. Tyvm. – Realitätsverlust Feb 11 '16 at 08:40
It's so simple, but note that this only works with PHP 5.4 or later. – Marcos Pérez Gude Feb 11 '16 at 08:41
if you call `someRandomClass::$fn` then `return $this->valueThis` will not work as you called it as statically? – Chetan Ameta Feb 11 '16 at 08:50
It works perfectly. Static functions are special because don't need instance, but it works without problems. See the #3rd example in the docs: http://php.net/manual/en/functions.variable-functions.php – Marcos Pérez Gude Feb 11 '16 at 08:54

score 1 · Answer 2 · answered Feb 11 '16 at 08:38

1

You can use variables' value for calling function like

function a(){ echo "Testing"; }
$b="a";
$b();

This is gonna echo Testing

answered Feb 11 '16 at 08:38

Batu.Khan

3,060
2
19
26

Calling different functions depending on the value of a given parameter

2 Answers2