Detailed explanation of file upload in php
Have you really mastered php file upload technology? This article has compiled relevant information on PHP file uploading for everyone. It has certain reference value. Interested friends can refer to it.
First of all, let me state that this chapter has a lot of content and is relatively difficult. , you have to have an attitude of fighting with yourself. Don’t miss the subtleties, practice more and more is the way to go.
Learning is like climbing a mountain. You have to do it step by step. First, set a small goal for yourself, and then continue to climb higher and higher, and finally reach the top.
Please consider the above two pieces of advice carefully
1. Description of my preparations.
Editor: sublime text3 (Which editor you use depends on your preference)
Server build: Use phpstudy2014 to build the server. The server file is stored in the www file on the D drive of my computer. (Installing phpstudy will automatically generate the www file, you decide which disk to install it on). Run phpstudy and enter localhost in the browser address bar to access files on the server.
The process of uploading files: The browser uploads the file on the client, click submit, the file is sent to a php file in the server for processing, and the php uploads the file Save the file to the server.
2. Create the form
Please see my html code
1. application/x-www-form-urlencoded: Form data is encoded as name/value pairs. This is a standard encoding format.
2. multipart/form-data: Form data is encoded as a message, and each control on the page corresponds to a part of the message.
3. text/plain: The form data is encoded in plain text, without any controls or formatting characters.
Supplement (just take a look): The enctype attribute of ORM is the encoding method. There are two commonly used ones: application/x-www-form-urlencoded and multipart/form-data. The default is application/x-www-form. -urlencoded. When the action is get, the browser uses the x-www-form-urlencoded encoding method to convert the form data into a string (name1=value1&name2=value2...), and then appends the string to the end of the url, splits it with ?, and loads it. this new url. When the action is post, the browser encapsulates the form data into the http body and then sends it to the server. If there is no type=file control, just use the default application/x-www-form-urlencoded. But if there is type=file, multipart/form-data will be used. The browser will divide the entire form into control units, and add Content-Disposition (form-data or file), Content-Type (default is text/plain), name (control name) and other information to each part, and Add delimiter (boundary).
In short, remember two sentences: if there is type=file in the input tag, then enctype=multipart/form-data. If there is no type=file, application/x-www-form-urlencoded is generally used.
When uploading files, the data must undergo certain transformations before they can be uploaded to the server. The difference between application/x-www-form-urlencoded and multipart/form-data is the conversion encoding method.
3. Create a php file to process the uploaded files.
FILES["myfile"]["error"]=1 The uploaded file exceeds the server limit, such as exceeding the server space size. _FILES["myfile"]["error"]=2 exceeds the browser limit for uploading $_FILES["myfile"]["error"]=3 Only part of the file is uploaded
Upload limit
Normally, the server usually limits the size or type of files uploaded by the server. We add restrictions on the uploaded file code based on the above php code.
First familiarize yourself with the usage of several functions:
explode()The function is used to split strings. For example: explode(“.”,”aaa.HTML”) is to divide this at the position of the dot. The string is divided into two strings, "aaa" and "HTML", and these two strings are stored in the same array in order.
end()Get the value of the last element in the array.
in_array() Search for an element in the array to see if it exists. It returns true if it exists and false if it does not exist.
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4. Save the uploaded file
After the file is uploaded, it is saved in a temporary location. It will disappear when the script ends. If we want to save it permanently on the server, we need to save it in another location.
. file_exists("upload/" . FILES["file"]["name"]) checks whether the file or directory exists. .moveuploadedfile(_FILES["file"]["tmp_name"], "upload/" . $_FILES["myfile"]["name"]);Move the uploaded file from the temporary location to the server space.
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The above is the entire content of this article, I hope it will be helpful to everyone's study.
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