Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Functions.php
public static function isFormula($value = '', Cell $pCell = null)
    {
        if ($pCell === null) {
            return self::REF();
        }

        return substr($pCell->getWorksheet()->getCell($value)->getValue(), 0, 1) === '=';
    }
public static function isFormula($value = '', Cell $pCell = null)
    {
        if ($pCell === null) {
            return self::REF();
        }

        return substr($pCell->getWorksheet()->getCell($value)->getValue(), 0, 1) === '=';
    }
public static function isFormula ( $ value = '' , Cell $ pCell = null ) { if ( $ pCell === null ) { return self :: REF ( ) ; } return substr ( $ pCell -> getWorksheet ( ) -> getCell ( $ value ) -> getValue ( ) , 0 , 1 ) === '=' ; }
ISFORMULA.

@param mixed $value The cell to check
@param Cell $pCell The current cell (containing this formula)

@return bool|string
ISFORMULA .