html代码：
实例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../jquery/jquery-3.2.1.min.js"></script>
<style>
fieldset{
width: 80%;
height: 600px;
margin: auto;
text-align: center;
font-weight: bolder;
font-size: 2em;
color: black;
background-color: #cccccc;
}
P{
font-size: 1em;
padding: 20px;
}
p>input{
font-size: 1.1em;
margin-left: 20px;
}
p >input:hover{
color: orange;
cursor: pointer;
}
p>label{
background-color: red;
}
button{
width: 200px;
height: 70px;
background-color: paleturquoise;
font-size: 40px;
color: slategray;
}
button >span{
font-size: 1.1em;
}
</style>
</head>
<body>
<form method="POST" enctype="multipart/form-data">
<input type="hidden" name="MAX_FILE_SIZE" value="500000000">
<fieldset>
<legend>上传文件</legend>
<p>
<label for="upload">上传文件</label><input type="file" name="upload" id="upload">
</p>
<p align="center">
<button type="submit" name="submit" id="submit">上传</button>
</p>
</fieldset>
</form>
<script>
$('#submit').click(function () {
// 1.获取文件对象
var file_data=$('#upload')[0].files[0]
//2.上传文件类型时要用FormData类
var formData = new FormData()
//3.添加文件对象
formData.append('upload',file_data)
//ajax处理事件
$.ajax({
url:'uploadPic.php',
type:'POST',
data:formData,
/**
* 必须false才会避开jQuery对 formdata 的默认处理
* XMLHttpRequest会对 formdata 进行正确的处理
*/
processData: false,
/**
*必须false才会自动加上正确的Content-Type 用于对data参数进行序列化处理 这里必须false
*/
contentType: false,
dataType:'json',
cache:false,//上传文件无需缓存
success: function (data) {
//数据状态为0 上传成功
if (data.status == 0) {
$('p').find('span').remove();
$('#submit').after('<span>').next().text(data.msg).css('color', 'green');
} else {
$('p').find('span').remove();
$('#submit').after('<span>').next().text(data.msg).css('color', 'red');
}
}
})
return false
})
</script>
</body>
</html>运行实例 »
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php代码（uploadPic.php）：
实例
<?php
// 1.检测请求是否是post
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
//2.检查是否有文件被上传
if (isset($_FILES['upload'])){
// 3.允许文件上传的类型
$allow=['image/jpg','image/jpeg','image/png'];
//4.上传文件的类型在这个$allow中
if (in_array($_FILES['upload']['type'],$allow)) {
if (is_uploaded_file($_FILES['upload']['tmp_name'])){
//5.将文件移动到临时目录
if (move_uploaded_file($_FILES['upload']['tmp_name'],"pic/{$_FILES['upload']['name']}")) {
exit(json_encode(['status'=>0,'msg'=>'上传成功！']));
}
}
} else {
exit(json_encode(['status'=>1,'msg'=>'选择文件类型错误']));
}
}
//对上传错误进行处理
if ($_FILES['upload']['error']>0) {
switch ($_FILES['upload']['error']) {
case 1:
exit(json_encode(['status'=>2,'msg'=>'文件超过了php.ini配置大小']));
break;
case 2:
exit(json_encode(['status'=>3,'msg'=>'文件超过了html表单配置大小']));
break;
case 3:
exit(json_encode(['status'=>4,'msg'=>'仅有部分文件上传']));
break;
case 4:
exit(json_encode(['status'=>5,'msg'=>'没有文件上传']));
break;
case 6:
exit(json_encode(['status'=>6,'msg'=>'没有可用的临时文件']));
break;
case 7:
exit(json_encode(['status'=>7,'msg'=>'磁盘已满']));
break;
case 9:
exit(json_encode(['status'=>8,'msg'=>'上传被终止！']));
break;
default:
exit(json_encode(['status'=>9,'msg'=>'未知错误']));
break;
}
//删除创建的临时文件，当然系统会自动清空
if (file_exists($_FILES['upload']['tmp_name']) && is_file($_FILES['upload']['tmp_name'])){
unlink($_FILES['upload']['tmp_name']);
}
}
} else {
exit(json_encode(['status'=>10,'msg'=>'不是POST上传']));
}运行实例 »
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运行效果图：
