Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Engine/Logger.php
public function writeDebugLog(...$args)
    {
        //    Only write the debug log if logging is enabled
        if ($this->writeDebugLog) {
            $message = implode($args);
            $cellReference = implode(' -> ', $this->cellStack->showStack());
            if ($this->echoDebugLog) {
                echo $cellReference,
                    ($this->cellStack->count() > 0 ? ' => ' : ''),
                    $message,
                    PHP_EOL;
            }
            $this->debugLog[] = $cellReference .
                ($this->cellStack->count() > 0 ? ' => ' : '') .
                $message;
        }
    }
public function writeDebugLog(...$args)
    {
        //    Only write the debug log if logging is enabled
        if ($this->writeDebugLog) {
            $message = implode($args);
            $cellReference = implode(' -> ', $this->cellStack->showStack());
            if ($this->echoDebugLog) {
                echo $cellReference,
                    ($this->cellStack->count() > 0 ? ' => ' : ''),
                    $message,
                    PHP_EOL;
            }
            $this->debugLog[] = $cellReference .
                ($this->cellStack->count() > 0 ? ' => ' : '') .
                $message;
        }
    }
Write an entry to the calculation engine debug log.