PHP Ajax图片未上传

Question

我正在尝试在php上上传图像，如果我单击并选择图像，我将无法上传图像，单击添加按钮后它将成功选择图像，这是行不通的。     
    通知：未定义索引：文件 16
中的 C：\ xampp \ htdocs \ simplesales \ add.php 中的文件     
    通知：未定义索引：文件 26
中的 C：\ xampp \ htdocs \ simplesales \ add.php 中的文件     
    通知：未定义索引： 28
行中的 C：\ xampp \ htdocs \ simplesales \ add.php 中的文件     上传文件时出错，请重试！

表格

<form role="form" id="frmCompany" enctype="multipart/form-data">
<div class="row">
    <div class="col-md-12">
        <div class="fileuploader fileuploader-theme-default">
 <input type="hidden" name="fileuploader-list-files_" value="[]">
      <input type="file" id="file" name="file" style="position: absolute; z-index: -9999; height: 0px; width: 0px; padding: 0px; margin: 0px; line-height: 0; outline: 0px; border: 0px; opacity: 0;">
            <div class="fileuploader-items"><ul class="fileuploader-items-list">
                </ul>
            </div>

            <div class="row">
                <div class="col-md-12">
                    <div class="pull-right">
                        <button type="button" id="save" class="btn btn-info" onclick="validate()">Save</button>
                        <button type="submit" class="btn btn-default" onclick="cancel()">Cancel</button>
                    </div>
                </div>
            </div>
        </div>
    </div>
</div>
</form>

jQuery

<script>

var isNew = true;
    function validate() {
        if ($("#frmCompany").valid())
        {
            var _url = '';
            var _data = '';
            var _method;
            if (isNew == true) {
                _url = 'add.php';
                _data = $('#frmCompany').serialize();
                _method = 'POST';
            }
            $.ajax({
                type: _method,
                url: _url,
                dataType: 'JSON',
                data: _data,
                success: function (data) {
                    var msg;
                    if (isNew)
                    {
                        msg="image Uploaded to the folder";
                    }
                    else{
                        msg="Error";
                    }
                    $.alert({
                        title: 'Success!',
                        content: msg,
                        type: 'green',
                        boxWidth: '400px',
                        theme: 'light',
                        useBootstrap: false,
                        autoClose: 'ok|2000'


                    });
                    isNew = true;
                },
                error: function (xhr, status, error) {
                    alert(xhr);
                    console.log(xhr.responseText);
                }
            });
        }
    }
    $('#file').fileuploader({
        limit: 1,
    });

</script>

PHP add.php

<?php
if ($_SERVER['REQUEST_METHOD'] == 'POST')
{
    if ($_FILES["file"]["error"] > 100) {
        echo "Return Code: " . $_FILES["file"]["error"] . "<br />";
    } else {

        $target_path = "uploads/";

        $target_path = $target_path . basename( $_FILES['file']['name']);

        if(move_uploaded_file($_FILES['file']['tmp_name'], $target_path)) {
            //echo "The file ".  basename( $_FILES['file']['name']).
            //  " has been uploaded";
            $name = $_FILES['file']['name'];

        } else{
            echo "There was an error uploading the file, please try again!";
        }
    }
}
?>