PHP super global variable $ _FILES array to record file upload relevant information.
1.file_uploads=on/off
Whether to allow http file upload
2.max_execution_time=30
The maximum allowed script execution time, more than this time will error
3.memory_limit=50M
The maximum amount of memory that can be allocated to set script, to prevent a runaway script used too much memory, this instruction is only set at compile time
to take effect in the case --enable-memory-limit signs
4.upload_max_filesize=20M
The maximum size allowed to upload a file, this instruction must be less than post_max_size
5.upload_tmp_dir
Upload file temporary storage directory
6.post_max_size=30M
Allow post way acceptable maximum size
$ _FILES [ 'myFile'] [ 'name'] original last name of the client file.
MIME type $ _FILES [ 'myFile'] [ 'type'] file, you need to provide support for the information, such as "image / gif".
$ _FILES [ 'myFile'] [ 'size'] has uploaded the file size in bytes.
$ _FILES [ 'myFile'] after [ 'tmp_name'] file is uploaded in the temporary files stored on the server name, usually the system default. It can be specified in the php.ini upload_tmp_dir, but using putenv () from setting is ineffective.
$ _FILES [ 'myFile'] [ 'error'] and the associated file upload status codes. [ 'Error'] was added in PHP 4.2.0. Here is its description :( they became constant after PHP3.0)
UPLOAD_ERR_OK
值：0; 没有错误发生，文件上传成功。
UPLOAD_ERR_INI_SIZE
值：1; 上传的文件超过了 php.ini 中 upload_max_filesize 选项限制的值。
UPLOAD_ERR_FORM_SIZE
值：2; 上传文件的大小超过了 HTML 表单中 MAX_FILE_SIZE 选项指定的值。
UPLOAD_ERR_PARTIAL
值：3; 文件只有部分被上传。
UPLOAD_ERR_NO_FILE
值：4; 没有文件被上传。
值：5; 上传文件大小为0.
文件被上传结束后，默认地被存储在了临时目录中，这时您必须将它从临时目录中删除或移动到其它地方，如果没有，则会被删除。
也就是不管是否上传成功，脚本执行完后临时目录里的文件肯定会被删除。
附：修改PHP上传文件大小限制的方法
1. 一般的文件上传,除非文件很小.就像一个5M的文件,很可能要超过一分钟才能上传完.
但在php中,默认的该页最久执行时间为 30 秒.就是说超过30秒,该脚本就停止执行.
这就导致出现 无法打开网页的情况.这时我们可以修改 max_execution_time
在php.ini里查找
max_execution_time
默认是30秒.改为
max_execution_time = 0
0表示没有限制
2. 修改 post_max_size 设定 POST 数据所允许的最大大小。此设定也影响到文件上传。
php默认的post_max_size 为2M.如果 POST 数据尺寸大于 post_max_size $_POST 和 $_FILES superglobals 便会为空.
查找 post_max_size .改为
post_max_size = 150M
3. 很多人都会改了第二步.但上传文件时最大仍然为 8M.
为什么呢.我们还要改一个参数upload_max_filesize 表示所上传的文件的最大大小。
查找upload_max_filesize,默认为8M改为
upload_max_filesize = 100M
另外要说明的是,post_max_size 大于 upload_max_filesize 为佳.
上传效果展示：
其他详细配置问题可以参考我写的这篇文章：http://blog.ncmem.com/wordpress/2019/08/09/php%E4%B8%8A%E4%BC%A0%E5%A4%A7%E6%96%87%E4%BB%B6%E9%85%8D%E7%BD%AE/