Efficient CSV Export in PHP for Large Datasets

CSV (Comma Separated Values) is a plain‑text format commonly used for data exchange.

If you only need to export data from Excel without advanced features, using a simple PHP CSV export is more efficient than PHPExcel.

Exporting about 200,000 rows typically takes 2–3 seconds.

The following PHP function demonstrates an efficient way to stream a CSV file directly to the browser, convert UTF‑8 strings to GBK to avoid garbled characters, and flush the output buffer every 100 000 rows to keep memory usage low.

/**
 * Export excel(csv)
 * @data Export data
 * @headlist First row, column names
 * @fileName Output Excel file name
 */
function csv_export($data = array(), $headlist = array(), $fileName) {
    header('Content-Type: application/vnd.ms-excel');
    header('Content-Disposition: attachment;filename="' . $fileName . '.csv"');
    header('Cache-Control: max-age=0');

    // Open PHP file handle, php://output means output directly to browser
    $fp = fopen('php://output', 'a');

    // Output Excel column names
    foreach ($headlist as $key => $value) {
        // CSV's Excel supports GBK encoding, must convert, otherwise garbled
        $headlist[$key] = iconv('utf-8', 'gbk', $value);
    }

    // Write column names to file handle
    fputcsv($fp, $headlist);

    // Counter
    $num = 0;

    // Flush output buffer every $limit rows, not too large nor too small
    $limit = 100000;

    // Process rows one by one to avoid memory waste
    $count = count($data);
    for ($i = 0; $i < $count; $i++) {
        $num++;

        // Flush buffer to prevent issues with too much data
        if ($limit == $num) {
            ob_flush();
            flush();
            $num = 0;
        }

        $row = $data[$i];
        foreach ($row as $key => $value) {
            $row[$key] = iconv('utf-8', 'gbk', $value);
        }

        fputcsv($fp, $row);
    }
}

Call csv_export($data, $headlist, $fileName) with your dataset, column headers, and desired file name to generate the download.