php - Call to undefined function AppHttpControllers [ function name ]

In my controller, I create a function getFactorial

public static function getFactorial($num)

{
    $fact = 1;
    for($i = 1; $i <= $num ;$i++)
        $fact = $fact * $i;
    return $fact;
}

Then, I use it like this

public function codingPuzzleProcess()
{

    $word     = strtoupper(Input::get('word'));
    $length   = strlen($word);
    $max_value = ($length * 26);
    $characters = str_split($word);

    $num = 1 ;
    $index = 1;


    sort($characters);

    foreach ( $characters as $character) {
        $num += getFactorial($index) * $index;
        $index ++;
    }

    return Redirect::to('/coding-puzzle')
        ->with('word', $word )

        ->with('num', $num )
        ->with('success','Submit successfully!');

}

For some reason, I keep getting this error

Call to undefined function App\Http\Controllers\getFactorial()

Can someone please teach me how to fix this error ?

Much appreciated in advance.

---

CodeController.php

namespace App\Http\Controllers;
use View, Input, Redirect;

class CodeController extends Controller {


    public function codingPuzzle()
    {
        return View::make('codes.puzzle');
    }


    public static function getFactorial($num)
    {
        $fact = 1;
        for($i = 1; $i <= $num ;$i++)
            $fact = $fact * $i;
        return $fact;
    }



    public function codingPuzzleProcess()
    {

        $word     = strtoupper(Input::get('word'));
        $length   = strlen($word);
        $max_value = ($length * 26);
        $characters = str_split($word);

        $num = 1 ;
        $index = 1;


        sort($characters);

        foreach ( $characters as $character) {
            $num += getFactorial($index) * $index;
            $index ++;
        }

        return Redirect::to('/coding-puzzle')
            ->with('word', $word )

            ->with('num', $num )
            ->with('success','Submit successfully!');

    }


}

Answer

say you define the static getFactorial function inside a CodeController

then this is the way you need to call a static function, because static properties and methods exists with in the class, not in the objects created using the class.

CodeController::getFactorial($index);

----------------UPDATE----------------

To best practice I think you can put this kind of functions inside a separate file so you can maintain with more easily.

to do that

create a folder inside app directory and name it as lib (you can put a name you like).

this folder to needs to be autoload to do that add app/lib to composer.json as below. and run the composer dumpautoload command.

"autoload": {
    "classmap": [
                "app/commands",
                "app/controllers",

                ............
                "app/lib"
    ]
},

then files inside lib will autoloaded.

then create a file inside lib, i name it helperFunctions.php

inside that define the function.

if ( ! function_exists('getFactorial'))
{

    /**
     * return the factorial of a number
     *
     * @param $number
     * @return string

     */
    function getFactorial($date)
    {
        $fact = 1;

        for($i = 1; $i <= $num ;$i++)
            $fact = $fact * $i;

        return $fact;


     }
}

and call it anywhere within the app as

$fatorial_value = getFactorial(225);