How to implement upload file function in php

How to implement file upload in PHP

1. Form part

Allow users to upload files, add an upload attribute to the declaration of the HTML form:

enctype = 'multipart/form-data'

The method of the form must be POST

The form option MAX_FILE_SIZE hidden field is used to limit the size of the uploaded file , it must be placed in front of the file form element, and the unit is bytes.

The code is as follows:

<form enctype=&#39;multipart/form-data&#39; id=&#39;aa&#39; name=&#39;aaa&#39; method=&#39;post&#39; action=&#39;xxx.php&#39;> 
<input type=&#39;hidden&#39; name=&#39;MAX_FILE_SIZE&#39; value=&#39;2621114&#39; /> 
<input name=&#39;upload_file&#39; type=&#39;file&#39; /> 
</form>

Related recommendations: "PHP Getting Started Tutorial"

2. Processing uploaded files

When uploading, PHP receives an array of information about the file, which can be found in the super global array $_FILES.

For example: If the name of the file input box in the form is upload_file, then all information about the file is included in the array $_FILES['upload_file'].

For example: The customer uploaded an image array value of "aaa.jpg" as follows:

name "p5pp.jpg" The name of the file when uploading

type "image/ jpeg" file type

tmp_name "/tmp/phpjksdf" The temporary file name on the server side

error The return value of upload error

size 2045 The actual size of the file

The errors in the above array will return different constant values, as follows:

UPLOAD_ERR_OK No error occurred, the file upload was successful

UPLOAD_ERR_INI_SIZE The file size exceeds the value limited by the upload_max_filesize option in PHP.INI

UPLOAD_ERR_FORM_SIZE The size of the uploaded file exceeds the MAX_FILE_SIZE option value in the HTML form. You can check the form $FILES ['up_file']['size'] in the program to handle

UPLOAD_ERR_PARTIAL Only part of the file was uploaded

UPLOAD_ERR_NO_FILE The user did not provide any file upload

Specific example of post-upload processing:

The code is as follows:

if(!move_uploaded_file($_FILES['f']['tmp_name'],"uploads/".$_FILES['f']['name'].".jpg")){ 
echo "error"; 
}

Function:

move_uploaded_file moves the uploaded temporary file to the specified directory

Example:

move_uploaded_file('temporary file name','specified file path')

is_uploaded_file determines whether it is a file uploaded through http Post

Example:

The code is as follows:

if(!is_uploaded_file($_FILES['f']['tmp_name'])){ 
echo '非法'; 
}

3. Related parameters

Parameters in php.ini that PHP uploads the design to:

file_uploads Whether to allow file uploads, default ON.

upload_tmp_dir Temporary directory for uploading files. If not specified, the system default location will be used.

upload_max_filesize The maximum size of allowed uploaded files, the default is 2M.

post_max_size controls the maximum amount of data that PHP can accept in a form submission using the POST method. If you want to use PHP files to upload, this value should be changed to be larger than upload_max_filesize.

max_input_time limits the time in seconds for receiving data through POST/GET/PUT methods.

memory_limit In order to avoid running scripts from using a large amount of system memory, PHP allows you to define memory usage limits. Set this parameter to specify the maximum memory capacity that a single script can use, which should be appropriately larger than the post_max_size value.

max_execution_time is used to set the time, in seconds, that PHP waits for the script to be executed before forcibly terminating the script. This second option can limit infinite loop scripts, but this feature can also cause the operation to fail when there is a long period of legitimate activity (such as uploading a large file). In this case, you must consider increasing this variable.

4. Consider multi-file upload

You can easily upload multiple files by using the $_FILES array. The $_FILES array can obtain all the file field contents in the client form, thereby obtaining all files uploaded in the same form.

5. Break through the upload memory limit

Method 1:

Modify the memory_limit value in php.ini to a larger value, such as 64M

Method 2:

Use the Apache Rewrite method to dynamically modify the value of memory_limit. First create a .htaccess file and save it in the current directory of the file upload program.

The code is as follows:

php_value memory_limit 100M 
php_value post_max_size 30M 
php_value upload_max_filesize 30M 
php_value max_execution_time 300 
php_value max_input_tim 300 
php_value display_errors On

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