extracting filename and path from an absolute path?

[sneakyimp]

ok, i'm familiar with the PHP routines pathinfo(), basename(), dirname(), etc. but i have a thornier question.

how can i create a function that will extract a filename or path name that is submitted by a FILE INPUT FIELD. as you may know, HTML forms support fileupload. unfortunately, windows machines use '\' as a separator, unix machines use '/' and macs used to use ':' although i have no idea what they use now.

i imagine this will require some kind of agent sniffing which i know nothing about in PHP. any help would be much appreciated. i've managed to write this routine which works OK to parse my windows URLs. i would love a foolproof one that is platform independent.

function GetFileNameFromFullPath($FullPath) {
	$result = strrchr($FullPath, "\\\\");
	$result = substr($result,1,strlen($result));
	return $result;
}

[mrhappiness]

in your php script you don't know where the user has stored the uploaded file at his own comp

you only get the filename

so you don't have to worry about all that stuff

[sneakyimp]

OK...my page is a little more complicated than i let on. basically i have a form and a preview pane. when the user browses for a file locally and selects one (i.e., the 'onchange' event of the file input is spring) i reload my preview window to show their file. this lets the user preview the file before uploading. the mechanism requires that i send the local path as an argument to my page IMAGE_PREVIEW.PHP which means that i do, in fact, have to parse a full path that will vary by client. the reason i need the filename is that i also check to see if the user has already uploaded a file by this name so i can warn them that they are about to overwrite a file.

[mrhappiness]

let me tell you something...

i not only know that html forms allow file uploads i know even more
every time you use a php script it get's executed at the webserver and therefor you have no access to the clien'ts local file system

if you submit he form to a php script for preview purposes the file get's uploaded too

if you don't want this to happen you have to deal with javascript

[sneakyimp]

thanks for your response

the file does not get uploaded and yes i'm dealing with javascript. i have two IFRAMES. one has a form input like this:

<INPUT TYPE=FILE NAME="uploaded_file" onchange="preview_local_file(this.value);">

the javascript routine reloads the other IFRAME with an argument like this:

function preview_local_file(localfile) {
window.frames['image_preview'].location = "image_preview.php?img=file://" + escape(localfile) + "&local=1";
}

the resulting code in the preview file needs to take that argument (img is a path on the user's machine to an image file) and display it. the resulting image tag looks something like this:

<IMG SRC="file://C:\my documents\images\my_image_file.gif">

the file does not get uploaded, it is merely displayed by referring to a local file. the problem i'm having is that windows machines will use backslashes, macs something else, etc. i need to check to see if the user has already uploaded a file with this name so that i don't overwrite it.