PHP file upload to determine if file has chosen to upload files

The following HTML code like

The code is as follows	Copy Code
<formaction= "?" Method= "POST" enctype= ' Multipart/form-data ' > File Upload: <inputtype= "file" name= "file" id= "file"/> <inputtype= "Submit" id= "send" value= "submitted"/> </form>

Our most commonly used in the front of the simple to judge

The code is as follows	Copy Code
<script> Varsend=document.getelementbyid ("send"); Send.onclick=function () { Varfile=document.getelementbyid ("File"). Value; if (file.length<1) { Alert (' Please select Picture '); Returnfalse; } } </script>

If we're going to do real security, we need to get in the background to judge.

The code is as follows	Copy Code
<?php Determine if the pic file box has selected a file if (!empty ($_files[' file '] [' tmp_name '])) { Echo ' selected file '; }else{ echo ' Please select file '; } Ps:$_files behind the [' tmp_name '] must not forget to write, it means to be a temporary meaning ?>

An analysis of an example

JS Judgment is more general we just use the File=document.getelementbyid ("file"). value to determine whether the file has a value or is not empty, so as long as you enter a number can be directly submitted, So we need to go into the user name restrictions such as uploading files

Such as

The code is as follows	Copy Code
Functioncheckworkfile () { Varobj=document.getelementbyid (' Fumain '); if (obj.value== ') { Alert (' Please select the work Book file to upload '); Returnfalse; } Varstuff=obj.value.match (/^ (. *) (\.) (. {1,8}) $/) [3]; if (stuff!= ' Doc ') { Alert (' file type is incorrect, please select. doc file '); Returnfalse; } Returntrue; }

For PHP processing We also only use if (!empty ($_files[' file ' [' Tmp_name '])) {To judge is not empty, in fact, this is not reasonable

If we can handle this

The code is as follows

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function File_type ($filename) { $file = fopen ($filename, "RB"); $bin = Fread ($file, 2); Read Only 2 bytes Fclose ($file); $strInfo = @unpack ("C2chars", $bin); $typeCode = Intval ($strInfo [' chars1 ']. $strInfo [' chars2 ']); $fileType = '; Switch ($typeCode) { Case 7790: $fileType = ' exe '; Break Case 7784: $fileType = ' midi '; Break Case 8297: $fileType = ' rar '; Break Case 8075: $fileType = ' zip '; Break Case 255216: $fileType = ' jpg '; Break Case 7173: $fileType = ' gif '; Break Case 6677: $fileType = ' bmp '; Break Case 13780: $fileType = ' png '; Break Default $fileType = ' Unknown: '. $typeCode; } Fix if ($strInfo [' chars1 ']== '-1 ' and $strInfo [' chars2 ']== ' -40 ') return ' jpg '; if ($strInfo [' chars1 ']== ' -119 ' and $strInfo [' chars2 ']== ') return ' PNG '; return $fileType; } echo file_type (' start.php '); 6063 or 6033

So that we can limit the upload file type, but also to the program to do a security process OH