Returning a method in PHP

Question

I have a class called Converter

class Converter {
  public function convert($value, $from, $to){
    $this->switchUnitCall($from)($value, $to);
  }

  private function switchUnitCall($from){
    switch($from){
      case 'm':
        return $this->fromM; break;
      case 'km':
        return $this->fromKM; break;
    }
  }

  private function fromM($value, $to){}
  private function fromKM($value, $to){}
}

I want to return the private method called fromM or fromKM to its caller, so I can call the fromM with my another custom arguments inside the convert method.

When I run the code above, I got error Undefined property: Converter::$fromM

My question, is it possible to return a method in PHP? and how is it done? Thank you.

Is this your actual case or an example, it may be better to put the switch/case in the convert method rather than having to pass it around. — Nigel Ren
– Nigel Ren, Commented Feb 26, 2020 at 17:26
I would recommend using a callable in return that accesses by method name: 3v4l.org/5tu01 — Jared Farrish
– Jared Farrish, Commented Feb 26, 2020 at 17:36

Maxim Sagaydachny · Accepted Answer · 2020-02-26 17:11:17Z

3

You can't return method but you can use method name to invoke it dynamically:

class Converter {
  public function convert($value, $from, $to){
    $method=$this->switchUnitCall($from);
    $this->$method($value, $to);
  }

  private function switchUnitCall($from){
    switch($from){
      case 'm':
        return "fromM"; break;
      case 'km':
        return "fromKM"; break;
    }
  }

  private function fromM($value, $to){}
  private function fromKM($value, $to){}
}

answered Feb 26, 2020 at 17:11

Maxim Sagaydachny

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Comments

Nikola Kirincic · Accepted Answer · 2020-02-26 19:21:44Z

1

You can return your method, but keep in mind the visibility of a specific method, and from which scope they can be called. These two methods are private and can be called only within the given class.

The problem with this code is that you have called your methods as properties, thus the error for the undefined property.

They should be called like methods with parentheses and 2 mandatory passed $this->fromM($value, $to), also you need to pass the arguments $value and $to to switchUnitCall() since they are mandatory too. Also, these two methods need to return a result:

 class Converter {
      public function convert($value, $from, $to){
        $this->switchUnitCall($from, $value, $to);
      }

      private function switchUnitCall($from, $value, $to){
        switch($from){
          case 'm':
            return $this->fromM($value, $to); 
            break;
          case 'km':
            return $this->fromKM($value, $to); 
            break;
        }
      }

      private function fromM($value, $to){
       //return conversion
      }
      private function fromKM($value, $to){
       //return conversion
      }
    }

edited Feb 26, 2020 at 19:21

answered Feb 26, 2020 at 17:26

Nikola Kirincic

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1 Comment

Fanny Hasbi Over a year ago

Thank you for your answer. Based on your code I've to code redundant parameter for each case, it will take a long time instead of once when I call it.

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