Detailed explanation of the implementation of PHP file upload function in 5 steps_PHP tutorial

1. The form part
allows users to upload files. An upload attribute must be added to the declaration of the HTML form:
enctype = multipart/form-data
The method of the form must be The POST
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, in bytes.
For example:

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 contained in the array $_FILES[upload_file]. " /tmp/phpjksdf" The temporary file name on the server side
error The return value of the upload error
size 2045 The actual size of the file

The error in the above array will return different constant values, as follows:
UPLOAD_ERR_OK No error occurred and the file was uploaded successfully
UPLOAD_ERR_INI_SIZE The file size exceeded the value of the upload_max_filesize option in PHP.INI
UPLOAD_ERR_FORM_SIZE The size of the uploaded file exceeded the MAX_FILE_SIZE option value in the HTML form. You can check the form $FILES [up_file][size] in the program to process
UPLOAD_ERR_PARTIAL Only part of the file was uploaded
UPLOAD_ERR_NO_FILE The user did not provide any file upload
Specific example of post-upload processing:
if( !move_uploaded_file($_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 the file is uploaded through http Post
Example:
if(!is_uploaded_file($_FILES[f][tmp_name])){
echo is illegal;
}


3. Related parameters

Parameters in php.ini designed for PHP upload:
file_uploads Whether to allow file uploads, default ONupload_tmp_dir Temporary directory to prevent file uploads, if not specified, use the system default locationupload_max_filesize Allow file uploads The maximum size, 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 file 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 defining memory usage limits. Set this parameter to specify the maximum memory capacity that a single script program can use, which should be appropriately larger than the post_max_size value
max_execution_time is used to set the time that PHP waits for the script to be executed before forcibly terminating the script, in seconds. 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 uploading multiple files

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 64MMethod 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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After reading the above article, I hope it will be helpful to you.



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