PHP upload principle and operation implementation, PHP upload principle
About PHP upload file function class Library, there are many packages on the Internet is perfect, we can directly use it.
This article is just about the upload principle and simple upload operation, the veteran will ignore ha ^_^ ~
There are some security judgments, such as: Server limit can receive image types of files, and the client maliciously to the virus file suffix name to image matching file upload.
(for example, single file upload, multi-file principle is still unchanged, but a little bit more tips)
DOCTYPE HTML Public "-//W3C//DTD XHTML 1.0 transitional//en" "http://www.w3.org/TR/xhtml1/DTD/ Xhtml1-transitional.dtd "><HTMLxmlns= "http://www.w3.org/1999/xhtml"Xml:lang= "en"><Head> <Metahttp-equiv= "Content-type"content= "Text/html;charset=utf-8"> <title>Upload files title>!-- Head ; < Body ; < form Action = "upload.php" enctype = "Multipart/form-data" Method = "POST" ; < input type = "hidden" name = "Max_file_size" value = "10000" /> Uploading Files: < input type = "File" name = "File" /> < input type = "Submit" value = "Upload" /> !-- form ; !-- Body ; !-- HTML ;
1. Form Tag Enctype Property
The enctype= "Multipart/form-data" in the form is the MIME encoding used to set up the form.
By default, this encoding format is application/x-www-form-urlencoded and cannot be used for file uploads;
Only the multipart/form-data is used and the submission method is Post for full file data transfer.
2. MAX_FILE_SIZE Hidden Fields
max_file_size hidden Fields (in bytes) must precede the file input field with a value of the maximum size of the received file. This is a suggestion for the browser, PHP will also check this.
This setting can be bypassed easily on the browser side, so do not expect this feature to block large files. (However, it is best to add this item to the form because it avoids the hassle of having to wait for a large file to be uploaded before the user discovers that the file is too large to upload.) )
upload.php
PHP print_r($_files);? >
We can see:
Array ( [fileArray ( = = Photo file. JPG = image/jpeg = F:\wamp\tmp\php41BB. TMP = 0 = 73886 ))
3. Application of global variable $_files
$_files[' file ' [' name '] is the original file name of the uploaded file
$_files[' file ' [' type '] is the MIME type of the uploaded file
$_files[' file ' [' size '] the size of the uploaded files, in bytes
$_files[' file ' [' Tmp_name '] files are uploaded and stored on the server after the temporary file name ()
$_files[' file ' [' Error '] upload error code
4, by default, the upload file will be saved in the server side of the temporary folder, its directory in the php.ini set
PHP.ini some common settings related to file uploads:
file_uploads; Whether to allow the switch to upload files over HTTP. The default is on, which is open
Upload_tmp_dir; Files are uploaded to the server where temporary files are stored, and if not specified, the system default Temp folder is used
upload_max_filesize; That is, the maximum size allowed for uploading files. Default is 2M
post_max_size; Refers to the maximum value that can be received by a form post to PHP, including all values in the form. Default is 8M
The following is a single file upload complete code, because it is random with write, may be a bit of logic nesting, understand the principle of the most important.
Php//Get upload file information $fileName=$_files[' File '] [' Name ']; $fileType=$_files[' File '] [' Type ']; $fileError=$_files[' File '] [' Error ']; $fileSize=$_files[' File '] [' Size ']; $tempName=$_files[' File '] [' Tmp_name '];//temp file name//definition upload file type $typeList=Array("Image/jpeg", "image/jpg", "Image/png", "image/gif");//define the allowed types if($fileError>0){ //Upload file error number judgment Switch($fileError) { Case1:$message= "The uploaded file exceeds the value of the Upload_max_filesize option limit in php.ini. "; Break; Case2:$message= "The size of the uploaded file exceeds the value specified by the Max_file_size option in the HTML form." "; Break; Case3:$message= "The file is only partially uploaded. "; Break; Case4:$message= "No files were uploaded." "; Break; Case6:$message= "The Temp folder could not be found." "; Break; Case7:$message= "File Write Failed"; Break; Case8:$message= "File upload interrupted due to PHP extension"; Break; } Exit("File Upload failed:".)$message); } if(!Is_uploaded_file($tempName)){ //determine if it is a post-uploaded file. Exit("not uploaded by HTTP POST"); }Else{ if(!In_array($fileType,$typeList)){ Exit("uploaded file is not a specified type"); }Else{ if(!getimagesize($tempName)){ //prevent users from uploading malicious files, such as changing the virus file name extension to picture format Exit("The uploaded file is not a picture"); } } if($fileSize>100000){ //limit the size of upload files for specific forms Exit("Upload file exceeds the limit size"); }Else{ //avoid uploading files in Chinese name garbled $fileName=Iconv("UTF-8", "GBK",$fileName);//Convert the character encoding Iconv crawled from utf-8 to GBK output $fileName=Str_replace(".", Time().".",$fileName);//Add a timestamp after the name of the image to avoid overwriting files with duplicate names if(Move_uploaded_file($tempName, "uploads/".$fileName)){ Echo"Upload the file successfully!" "; }Else{ Echo"Upload file Failed"; } } }?>
5, about the PHP upload files of some common functions: (The specific usage is not posted out, look at the API document Bar ^_^)
file_exists Checking whether a file or directory exists
is_uploaded_file To determine if the file was uploaded via HTTP POST
move_uploaded_file Moving uploaded files to a new location
is_writable Determines whether a given file name can be written
iconv character encoding for mutual transfer
str_replace string substitution (change filename, anti-duplicate name)
getimagesize Check if it is a picture file (other types of files can be detected even if the suffix name is changed)
PHP implementation Log management (record user action) principle
The implementation of the implementation of the log and operation log, the number of custom 2 functions, when the user login and add, modify and delete do the two functions respectively. The information is recorded in the database table.
PHP file upload, how to achieve progress bar work can?
Not so troublesome, jquery has a lot of plug-ins to achieve the upload file progress style, you can use the next
PS: Since you are so personality, I will give you the principle of implementation, specific details you do it yourself.
Normal page access is all synchronous, is the request-to-feedback, and the progress bar needs real-time data, so the normal page is not able to achieve this function, it is necessary to use the asynchronous Ajax cycle to obtain progress data, the source of course is the server sent, so that encountered a serious problem, PHP does not get the status of the file transfer process. Fortunately, the PHP founder wrote an APC extension (another extension is uploadprogress), using the extended syntax, plus Ajax, using the JS operation of the DOM object page, the implementation of the progress bar.
You understand the principle, you can hardly make it, eh.
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