How to insert millions of rows to the database with PHP (YT Tutorial)

insert_many_rows.php

<?php

class Stock {

    public function store_stock_history()
    {
        $date = date('Y-m-d');
    
        $files = File::files(app_path() . '/resources/historical_lists/' . $date);
    
        $completed_stocks = DB::table('stocks')
            ->select('symbol')
            ->where('history_updated', $date)
            ->groupBy('symbol')
            ->orderBy('symbol', 'asc')
            ->get();
    
        $completed_symbols = array_pluck($completed_stocks, 'symbol');
    
        foreach ($files as $file)
        {
            $symbol = basename($file, '.csv');
    
            if (in_array($symbol, $completed_symbols)) continue;
    
            $handle = fopen($file, "r");
    
            while( ! feof($handle))
            {
                // the stock's daily summary (closing price, volume, etc.)
                $summary = fgetcsv($handle);
    
                // 1. continue to next iteration if it's the header
                // 2. continue to next iteration if there isn't seven elements (invalid record)
                if ($summary[0] == 'Date' || count($summary) !== 7) continue;
    
                // if the date is less than today, we've already stored it, break out of the loop
                if (remove_whitespace($summary[0]) < $date) break;
    
                DB::table('summaries')->insert([
                    'date'   => remove_whitespace($summary[0]),
                    'symbol' => remove_whitespace($symbol),
                    'open'   => remove_whitespace($summary[1]),
                    'high'   => remove_whitespace($summary[2]),
                    'low'    => remove_whitespace($summary[3]),
                    'close'  => remove_whitespace($summary[4]),
                    'adjusted_close' => remove_whitespace($summary[6]),
                    'volume' => remove_whitespace($summary[5]),
                    'updated_at' => new Datetime,
                ]);
    
                print "Inserted: " . $symbol . ". Date: " . $summary[0] . PHP_EOL;
            }
    
            fclose($handle);
    
            DB::table('stocks')
                ->where('symbol', $symbol)
                ->update([
                    'history_updated' => $date,
                ]);
    
            print "--------------------------------". PHP_EOL;
            print "Finished inserting for: " . $symbol . PHP_EOL;
            print "--------------------------------". PHP_EOL;
        }
    }
}