Gravity Forms AJAX提交后如何启动文件下载

Question

我有一个重力表单，用户可以在其中设置复选框来选择要下载的文件。对于增强的 UX，表单是多页的并使用 AJAX。

使用以下 PHP 函数和 Gravity Forms Hook，我能够循环选中复选框并将文件添加到 ZIP 存档中，但目前无法开始下载。

add_filter( 'gform_after_submission_3', 'download_brochures_message', 10, 4 );
function download_brochures_message( $entry ) {

$confirmation = "Your download should begin shortly. \r\n";
$error = "Files not set \r\n";

$file1 = rgar( $entry, '1.1' );
$file2 = rgar( $entry, '1.2' );
$file3 = rgar( $entry, '1.3' );
$file4 = rgar( $entry, '1.4' );

$files = array(
        $file1,
        $file2,
        $file3,
        $file4
    );

print_r($files);

$zip = new ZipArchive();

$current_time = time();

$file_folder = wp_upload_dir();

$dir = $file_folder['path'];

$zip_file = tempnam( $dir, time() );

$zip->open( $zip_file, ZipArchive::CREATE );

foreach ($files as $file) {
    $zip->addFile($file);
}

$zip->close();

echo $zip_file;

header('Content-disposition: attachment; filename="'.$zip_name.'"');
header('Content-type: application/zip');
header('Content-Length: ' . filesize($zip_file));
header("Location: $zip_file");
readfile($zip_file);
}

由于表单通过 AJAX 提交，页面标题已经发送，我收到的 PHP 错误是“无法修改标题信息 - 标题已发送”。如何修改此代码以允许 zip 下载？

Answer 1

要实现一个完全有效的解决方案，需要 PHP 后端函数来处理基于 POST 表单值的创建 zip，并使用少量 JavaScript 来启动下载。

PHP：

/**
 * Function to force file download based on user selected checkboxes.
 */
add_filter( 'gform_confirmation_{your-form-id}', 'get_chosen_brochures', 10, 4 );
function get_chosen_brochures( $confirmation, $form, $entry, $ajax ) {
    $brochures = retrieve_brochure_data( $entry );
    $confirmation = start_brochures_download( $brochures );
    return $confirmation;
}

function retrieve_brochure_data( $entry ){
    $radio_value_1 = rgar( $entry, '1.1' );
    $radio_value_2 = rgar( $entry, '1.2' );
    $radio_value_3 = rgar( $entry, '1.3' );
    $radio_value_4 = rgar( $entry, '1.4' );

    return array(
            $radio_value_1,
            $radio_value_2,
            $radio_value_3,
            $radio_value_4
        );
}

function start_brochures_download( $brochures ) {
    $files = $brochures;
    $error = "Files not set";
    $success = "Thank you. Your download will being shortly.";
    if( $files ) {

        $zip = new ZipArchive();

        $current_time = time();

        $file_name = "Archive-Name-".$current_time.".zip";

        $file_folder = wp_upload_dir();
        $dir = $file_folder['path'];
        $url = $file_folder['url'];
        $zip_file = $dir.'/'.$file_name;
        $zip_url = $url.'/'.$file_name;

        $zip->open( $zip_file, ZipArchive::CREATE );

        foreach ($files as $key => $file) {
            if( !empty($file) ){
                # download file
                $download_file = file_get_contents($file);

                #add it to the zip
                $zip->addFromString(basename($file), $download_file);
            }
            $error .= "\n *File $key is empty";
        }

        $zip->close();

        return $success . " If your download doesn't begin automatically, you can click <a id='generated-download-link' href='{$zip_url}'>here to start the download</a>.";

    } else {
        return $error;
    }
}

JS：

$(document).bind('gform_confirmation_loaded', function(event, formId){
    if( formId === 3 ){
        var download_url = $("#generated-download-link").attr('href');
        if(download_url) {
            var delay = 2000;
            setTimeout( function(){ window.location = download_url; }, delay );
        }
    }
});

我的初始代码问题的最大部分与我无法在页面加载后更改页眉有关。这是使用 AJAX 表单的一个限制，但是由于一些 UX 流程已经到位，所以 AJAX 是必需的。

要重复使用此代码，您需要将单选按钮或复选框值设置为您希望下载的文件的 URL。