public function getImplementedFunctionNames()
    {
        $returnValue = [];
        foreach (self::$phpSpreadsheetFunctions as $functionName => $function) {
            if ($this->isImplemented($functionName)) {
                $returnValue[] = $functionName;
            }
        }

        return $returnValue;
    }
public function getImplementedFunctionNames()
    {
        $returnValue = [];
        foreach (self::$phpSpreadsheetFunctions as $functionName => $function) {
            if ($this->isImplemented($functionName)) {
                $returnValue[] = $functionName;
            }
        }

        return $returnValue;
    }
public function getImplementedFunctionNames ( ) { $ returnValue = [ ] ; foreach ( self :: $ phpSpreadsheetFunctions as $ functionName => $ function ) { if ( $ this -> isImplemented ( $ functionName ) ) { $ returnValue [ ] = $ functionName ; } } return $ returnValue ; }
Get a list of implemented Excel function names.

@return array
Get a list of implemented Excel function names .