PHP file upload

File Upload Overview

The file upload function is a function often used in online life. File upload can be easily achieved using PHP. The specific process is as follows:

Select file in form-> Check file size and type-> Generate temporary file-> Move temporary file to file storage directory-> ; Record file information for easier management.

In the file upload function, the following issues need to be considered:

1. Limit the size of the uploaded file

2. Limit the type of the uploaded file

3. Only allow trusted users to upload files and prevent remote submission

4. Server-side file storage directory

5. Management of files after uploading

Through PHP , you can upload files to the server.

The examples in this chapter are completed under the test project. The directory structure is:

test

|-----upload #Directory for file upload

|-----form.html #Form file

|-----upload_file.php #php upload code

Source code download

Create a file upload form

It is very useful to allow users to upload files from a form.

Please look at the HTML form for uploading files below:

   php中文网(php.cn) 
   文件名：

Save the above code into the form.html file.

Some notes about the above HTML form are listed below:

The enctype attribute of the

tag specifies which content type to use when submitting the form. Use "multipart/form-data" when your form requires binary data, such as file content.

The type="file" attribute of the tag specifies that the input should be processed as a file. For example, when previewing in a browser, you'll see a browse button next to the input box.

Note: Allowing users to upload files is a huge security risk. Please allow only trusted users to perform file upload operations.

Create upload script

The "upload_file.php" file contains the code for uploading files:

 0) { echo "错误：" . $_FILES["file"]["error"] . "
"; } else { echo "上传文件名: " . $_FILES["file"]["name"] . "
"; echo "文件类型: " . $_FILES["file"]["type"] . "
"; echo "文件大小: " . ($_FILES["file"]["size"] / 1024) . " kB
"; echo "文件临时存储的位置: " . $_FILES["file"]["tmp_name"]; } ?>

By using PHP's global array $_FILES, you can upload files from the client computer to the remote server.

The first parameter is the input name of the form, and the second subscript can be "name", "type", "size", "tmp_name" or "error". As shown below:

$_FILES["file"]["name"] - The name of the uploaded file

$_FILES["file"]["type"] - The type of the uploaded file

$_FILES["file"]["size"] - The size of the uploaded file in bytes

$_FILES["file"]["tmp_name"] - Stored on the server The name of the temporary copy of the file

$_FILES["file"]["error"] - Error code caused by file upload

This is a very simple way to upload files. For security reasons, you should add restrictions on who is allowed to upload files.

Upload restrictions

In this script, we have added restrictions on file uploads. Users can only upload .gif, .jpeg, .jpg, .png files, and the file size must be less than 200 kB:

 0) { echo "错误：: " . $_FILES["file"]["error"] . "
"; } else { echo "上传文件名: " . $_FILES["file"]["name"] . "
"; echo "文件类型: " . $_FILES["file"]["type"] . "
"; echo "文件大小: " . ($_FILES["file"]["size"] / 1024) . " kB
"; echo "文件临时存储的位置: " . $_FILES["file"]["tmp_name"]; } } else { echo "非法的文件格式"; } ?>

Save the uploaded file

above The instance creates a temporary copy of the uploaded file in the server's PHP temporary folder.

This temporary copy file will disappear when the script ends. To save the uploaded file, we need to copy it to another location:

 0) { echo "错误：: " . $_FILES["file"]["error"] . "
"; } else { echo "上传文件名: " . $_FILES["file"]["name"] . "
"; echo "文件类型: " . $_FILES["file"]["type"] . "
"; echo "文件大小: " . ($_FILES["file"]["size"] / 1024) . " kB
"; echo "文件临时存储的位置: " . $_FILES["file"]["tmp_name"] . "
"; // 判断当期目录下的 upload 目录是否存在该文件 // 如果没有 upload 目录，你需要创建它，upload 目录权限为 777 if (file_exists("upload/" . $_FILES["file"]["name"])) { echo $_FILES["file"]["name"] . " 文件已经存在。 "; } else { // 如果 upload 目录不存在该文件则将文件上传到 upload 目录下 move_uploaded_file($_FILES["file"]["tmp_name"], "upload/" . $_FILES["file"]["name"]); echo "文件存储在: " . "upload/" . $_FILES["file"]["name"]; } } } else { echo "非法的文件格式"; } ?>

The above script detects whether the file already exists. If it does not exist, it copies the file to a directory named "upload" Down.

The file upload demonstration operation is as follows: