Why does mkdir not work without recursion set to true? - php

Question

I was fiddling with my code, trying to write some code that will take data(including pictures) uploaded from a form via POST which will then create a directory complete with its associated subdirectories to store the image.
While writing the code, i kept getting the error
Warning: mkdir(): No such file or directory in C:\Users\Admin\Desktop\UniServer\www\AddItem.php on line 94
HOWEVER, when i set mkdir's resursion to true, mkdir suddenly works and the directory is created without any problems.
My Code:
if(isset($_FILES['upload']['tmp_name']))
{
$numfile=count($_FILES['upload']['tmp_name']);
{
for($i=0;$i<$numfile;$i++)
{
if(is_uploaded_file($_FILES['upload']['tmp_name'][$i]))
{
//Conditionals for uploaded file
$foldername=$_SESSION['UserId'];
$cat=$_POST['category'];
$sub=$_POST['subcat'];
$itemname=$_POST['itemname'];
$allowed_filetypes=array('.jpg','.gif','.bmp','.png');
$max_filesize = 2097152; // Maximum filesize in BYTES (currently 2.0MB).
$upload_path = 'C:\Users\Admin\Desktop\UniServer\www\images\\'.$foldername.'\\'.$cat.'\\'.$sub.'\\'.$itemname.'\\'; // The place the files will be uploaded to.
//Checks if Folder for User exists
//If not, A folder for the user is created to store the user's images
if(!file_exists($upload_path))
{
$upload_path=mkdir($upload_path,0644,true);<-- This is the line
}
$filename = $_FILES['upload']['name'][$i]; // Get the name of the file (including file extension).
$ext = substr($filename, strpos($filename,'.'), strlen($filename)-1); // Get the extension from the filename.
// Check if the filetype is allowed, if not DIE and inform the user.
if(!in_array($ext,$allowed_filetypes))
{
die('The file you attempted to upload is not allowed.');
}
// Now check the filesize, if it is too large then DIE and inform the user.
if(filesize($_FILES['upload']['tmp_name'][$i]) > $max_filesize)
{
die('The file you attempted to upload is too large.');
}
// Check if we can upload to the specified path, if not DIE and inform the user.
if(!is_writable($upload_path))
{
$errormsg="Image Upload Failed.";
}
if(!move_uploaded_file($_FILES['upload']['tmp_name'][$i],"$upload_path" . $filename))
{
$errormsg= 'Your file upload was successful, view the file here'; // It worked.
}
}
}
}
}
else{echo"Upload failed";}
While my code is working now that i've set recursion to true, i still DON't understand exactly WHY it is working, so i would really appreciate it if someone could explain why exactly my code is working.
The closest i've come is with Why mkdir fails with recursive option set true?
Though i couldnt understand any of what was said in the link.
Thanks!

Answer 1

The mkdir() needs the recursive set to true since you ask it to create nested directories that do not exist, i.e.:
$upload_path = 'C:\Users\Admin\Desktop\UniServer\www\images\\'.$foldername.'\\'.$cat.'\\'.$sub.'\\'.$itemname.'\\';
So since the variable $foldername gets its value from the user session, if the user session change it changes. The same goes for the rest of the $upload_path parts, if something of them changes you have to create the whole path. Only the last part of the path ($itemname) can change without using the recursive option.

Answer 2

It fails because it parses the path provided as argument and "changes" path to parent of new directory.
Try this (in a folder test with a subfolder s):
mkdir s/s2/s3 <- will fail because s2 does not exist in s
mkdir s/s2 <- ok
mkdir s/s2/s3 <- ok
When calling with recursive set to TRUE, it does something different: splits the path as usual, but checks existence of each prefix.
Again in folder test:
mkdir -p s/s1/s2/s3/s4 will yield the following prefixes:
s
s/s1
s/s1
s/s1/s2
s/s1/s2/s3
s/s1/s2/s3/s4
Note: I've used mkdir under linux and p argument tells it to create parent directories if they do not exist (same as recursive).