PHP: assign function to class method

Question

How can I assign a function to a method in a class in PHP? I tried the following:

class Something{
    public function __construct(){
        $functionNames = array('foo', 'bar')

        $variable = 'blablabla';

        foreach($functionNames as $functionName){
            if(method_exists($this, $functionName))
                continue;

            $this->{$functionName}() = function($params){ //should create the methods "foo" and "bar"
                echo $variable; //should echo 'blablabla' (I know that the variable was declared outside this function, but how can I access it anyway?)
            }; //the error points to here
        }
    }
}

But this code gives me this error:

Fatal error: Can't use method return value in write context

Does anyone know how I can assign the anonymous function to the class method, while also still being able to access variables outside that function?

I do not think that is possible in PHP in the way that you are doing it. I think you have to instantiate an object or have a function return something that assigns something to a variable. Not a bad question though. — Mr. Concolato
– Mr. Concolato, Commented Dec 26, 2014 at 19:52
You can't return in a class constructor. It'll throw an error. php.net/manual/en/language.oop5.decon.php — versalle88
– versalle88, Commented Dec 26, 2014 at 19:53
@versalle88 yeah, that's true... I actually have a foreach loop and the return; is a continue;, but I decided to simplify the code a bit since (I thought) it wasn't necessary. I'll edit it though — Jonan
– Jonan, Commented Dec 26, 2014 at 19:56
Although it still won't work, when you assign an anonymous function, you should not use braces on the variable: $this->{$functionName[0]} = function($params){ — jeroen
– jeroen, Commented Dec 26, 2014 at 20:07
I don't see how this can work. Where is the value of $variable going to be stored once the constructor returns? — superultranova
– superultranova, Commented Dec 26, 2014 at 20:09

gen_Eric · Accepted Answer · 2014-12-26 20:24:28Z

You are doing foreach($functionNames as $functionName){ which means that $functionName is a string, not an array. So, don't use $functionName[0].

method_exists takes 2 parameters. One is the object and the other is the method name. It should be:

method_exists($this, $functionName)

As for creating the function, you don't need () on the left side of the =. It should be:

$this->$functionName = function($params) use($variable){
    echo $variable;
};

The use($variable) is needed to tell PHP to use that variable inside the function. That's how closures work in PHP, it's different than other languages.

So, your class should look like:

class Something{
    public function __construct(){
        $functionNames = array('foo', 'bar');

        $variable = 'blablabla';

        foreach($functionNames as $functionName){
            if(method_exists($this, $functionName)){
                continue;
            }

            $this->$functionName = function($params) use($variable){
                echo $variable;
            };
        }
    }
}

Problem here is that in this way of making functions, you are not actually creating a class method, but instead creating a class variable that contains a function.

So, you need to call it like so:

$test = new Something;
$foo = $test->foo;

$foo('abc');

You can't just do $test->foo('abc');.

EDIT: Another thing you can do is use PHP's __call "magic method". This will be ran whenever you do ->funcName(), regardless of whether the method exists or not. Using that method, you can just check to see if the method called was 'foo' or 'bar'. See this example:

class Something{
    private $variable;

    public function __construct(){
        $this->variable = 'blablabla';
    }

    public function __call($name, $params=array()){
        if(method_exists($this, $name)){
            // This makes sure methods that *do* exist continue to work
            return call_user_func(array($this, $name), $params);
        }
        else{
            $functionNames = array('foo', 'bar');

            if(in_array($name, $functionNames)){
                // You called ->foo() or ->bar(), so do something
                // If you'd like you can call another method in the class
                echo $this->variable;
            }
        }
    }
}

With this, now you can do the following:

$test = new Something;
$test->foo('abc');  // Will echo "blablabla"

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