Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Writer/Xls/Parser.php
public function parse($formula)
    {
        $this->currentCharacter = 0;
        $this->formula = $formula;
        $this->lookAhead = isset($formula[1]) ? $formula[1]
        : '';
        $this->advance();
        $this->parseTree = $this->condition();

        return true;
    }
public function parse($formula)
    {
        $this->currentCharacter = 0;
        $this->formula = $formula;
        $this->lookAhead = isset($formula[1]) ? $formula[1]
        : '';
        $this->advance();
        $this->parseTree = $this->condition();

        return true;
    }
The parsing method. It parses a formula.

@param string $formula the formula to parse, without the initial equal
sign (=)

@return mixed true on success