Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Writer/Xls/Parser.php
private function func()
    {
        $num_args = 0; // number of arguments received
        $function = strtoupper($this->currentToken);
        $result = ''; // initialize result
        $this->advance();
        $this->advance(); // eat the "("
        while ($this->currentToken != ')') {
            if ($num_args > 0) {
                if ($this->currentToken == ',' || $this->currentToken == ';') {
                    $this->advance(); // eat the "," or ";"
                } else {
                    throw new WriterException("Syntax error: comma expected in function $function, arg #{$num_args}");
                }
                $result2 = $this->condition();
                $result = $this->createTree('arg', $result, $result2);
            } else { // first argument
                $result2 = $this->condition();
                $result = $this->createTree('arg', '', $result2);
            }
            ++$num_args;
        }
        if (!isset($this->functions[$function])) {
            throw new WriterException("Function $function() doesn't exist");
        }
        $args = $this->functions[$function][1];
        // If fixed number of args eg. TIME($i, $j, $k). Check that the number of args is valid.
        if (($args >= 0) and ($args != $num_args)) {
            throw new WriterException("Incorrect number of arguments in function $function() ");
        }

        $result = $this->createTree($function, $result, $num_args);
        $this->advance(); // eat the ")"
        return $result;
    }
private function func()
    {
        $num_args = 0; // number of arguments received
        $function = strtoupper($this->currentToken);
        $result = ''; // initialize result
        $this->advance();
        $this->advance(); // eat the "("
        while ($this->currentToken != ')') {
            if ($num_args > 0) {
                if ($this->currentToken == ',' || $this->currentToken == ';') {
                    $this->advance(); // eat the "," or ";"
                } else {
                    throw new WriterException("Syntax error: comma expected in function $function, arg #{$num_args}");
                }
                $result2 = $this->condition();
                $result = $this->createTree('arg', $result, $result2);
            } else { // first argument
                $result2 = $this->condition();
                $result = $this->createTree('arg', '', $result2);
            }
            ++$num_args;
        }
        if (!isset($this->functions[$function])) {
            throw new WriterException("Function $function() doesn't exist");
        }
        $args = $this->functions[$function][1];
        // If fixed number of args eg. TIME($i, $j, $k). Check that the number of args is valid.
        if (($args >= 0) and ($args != $num_args)) {
            throw new WriterException("Incorrect number of arguments in function $function() ");
        }

        $result = $this->createTree($function, $result, $num_args);
        $this->advance(); // eat the ")"
        return $result;
    }
It parses a function call. It assumes the following rule:
Func -> ( Expr [,Expr]* ).

@return mixed The parsed ptg'd tree on success