How to implement file download in PHP?

Implementing file downloads in PHP usually involves the following steps:

1. Make sure the file exists and is available for download: First, you need to make sure the file you want to download exists and has the appropriate file permissions. You can use thefile_exists function to check if the file exists.

2. Set HTTP response headers: Before sending the file to the client, you need to set the correct HTTP response header to ensure that the file is delivered to the browser as a download. The following is sample code for setting response headers:

$file_path = '/path/to/your/file/filename.ext'; // 替换为要下载的文件的路径

if (file_exists($file_path)) {
    
    
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename="' . basename($file_path) . '"');
    header('Expires: 0');
    header('Cache-Control: must-revalidate');
    header('Pragma: public');
    header('Content-Length: ' . filesize($file_path));
    readfile($file_path);
    exit;
} else {
    
    
    echo '文件不存在或无法访问。';
}

3. Specify the file path: In the above code, replace the value of the $file_path variable with the actual path of the file you want to download.

4. Send file content: Use thereadfile function to send the file content to the client. This sends the contents of the file to the browser, causing it to begin downloading.

5. Exit the script: Once the file download is complete, exit the script via the exit function or the die function to ensure that no Other content will continue to be output after the file is downloaded.

The above code will tell the browser to download the file as an attachment instead of opening it directly in the browser. The user will see the browser's download dialog and can choose to save the file or open it, depending on the browser settings.

Please note that this is just a basic example, and actual applications may require more processing, such as file type verification, security checks, etc. Additionally, ensure that only authorized users can download files to prevent unauthorized access.