文件上传

代码如下

<!--文件上传请求必须是POST-->
<!--允许数据类型必须是multipart/form-data-->
<!--action三种写法-->
<!--1.空-->
<!--2.当前脚本-->
<!--3.现在用的  -->
<form action="<?php echo htmlspecialchars( $_SERVER['PHP_SELF'])?>" method="post" enctype="multipart/form-data">
<input type="hidden" name="file-size" value="542488">
    <fieldset>
        <legend align="center">文件上传</legend>
        <p><strong>选择文件：</strong><input type="file" name="upload"></p>
    </fieldset>
    <p><button type="submit" name="submit">上传</button></p>
</form>
<?php
//$_FILES:二维数组
//$_FILES['当前上传文件的控件名称，input[name="upload"]']
//$_FILES['upload']['name']文件原始名称
//$_FILES['upload']['type']文件类型
//$_FILES['upload']['size']文件大小
//$_FILES['upload']['tmp_name']服务器上临时文件夹
//$_FILES['upload']['error']错误代码
if ($_SERVER['REQUEST_METHOD']=='POST') {
    //判断是否有文件上传
    if (isset($_FILES['upload'])) {
        $allow = ['image/jpg','image/jpeg', 'image/png'];
        if (in_array($_FILES['upload']['type'], $allow)) {
            if (move_uploaded_file($_FILES['upload']['tmp_name'], "upload/{$_FILES['upload']['name']}")) {
                echo '<script>alert("上传成功")</script>';
            }

        } else {
            echo '<script>alert("上传文件格式不对")</script>';
        }
    }
    if ($_FILES['upload']['error'] > 0) {
        echo '<p>错误原因：<strong>';
        switch ($_FILES['upload']['error']) {
            case 1:
                echo '文件超过大小';
                break;
            case 2:
                echo '文件超过了表单中常量设置的大小';
                break;
            case 3:
                echo '仅有部分文件被上传';
                break;
            case 4:
                echo '没有文件被上传';
                break;
            case 6:
                echo '没有可用的临时文件夹';
                break;
            case 7:
                echo '磁盘已满,写入失败';
                break;
            case 8:
                echo '上传意外中止';
                break;
            default:
                echo '未知错误';
                break;
        }
        echo '</strong></p>';
        if (file_exists($_FILES['upload']['tmp_name']) && is_file($_FILES['upload']['tmp_name'])) {
            unlink($_FILES['upload']['tmp_name']);
        }
    }else {
        echo '1';}
}

?>

样式如下手写如下