PHP到AJAX，仅出现一个复选框

Question

当选择多个这样的值时出现此错误： https://lh3.googleusercontent.com/-D1oucKVR7rA/W0_PM1Po-9I/AAAAAAAAAjU/pWAGZCFY8cg6nHK6ALTWwSvZ38QdmsiqQCL0BGAYYCw/h544/2018-07-18.png https://lh3.googleusercontent.com/-jC8w5UQTKvg/W0_PNj03yJI/AAAAAAAAAjU/JBTRKBdb0_Eha5-yhVJa5F9F8B1PfY6lACL0BGAYYCw/h314/2018-07-18.png

它仅显示第一个复选框。 一段代码：

for (i in json['shipping_method']) {
                    html += '<p><strong>' + json['shipping_method'][i]['title'] + '</strong></p>';

                    if (!json['shipping_method'][i]['error']) {
                        for (j in json['shipping_method'][i]['quote']) {
                            html += '<div class="radio">';
                            html += '  <label>';

                            if (json['shipping_method'][i]['quote'][j]['code'] == '<?php echo $shipping_method; ?>') {
                                html += '<input type="radio" name="shipping_method[]" value="' + json['shipping_method'][i]['quote'][j]['code'] + '" checked="checked" />';
                            } else {
                                html += '<input type="radio" name="shipping_method[]" value="' + json['shipping_method'][i]['quote'][j]['code'] + '" />';
                            }

                            html += json['shipping_method'][i]['quote'][j]['title'] + ' - ' + json['shipping_method'][i]['quote'][j]['text'] + '</label></div>';
                        }
                    } else {
                        html += '<div class="alert alert-danger">' + json['shipping_method'][i]['error'] + '</div>';
                    }
                }