upload php check the file name duplicat

STEP 3
CHECK THE DUPLICAT NAME OF FILES ON YOUR SERVER


If we don't do this validation on upload script we will have a unpleasant situation . A file with the same name will be rewritten into the upload folder with the new one. To avoid such situations we have to do the following validation:



First we have to replace the empty space from name of files in upload.php  
 
//==================

$file_name = $_FILES['userfile']['name'];
$file_name = str_replace(' ', '_', $file_name);

//==================
 

Then we will check the existence of a file with the same name:
 

//==================
if (file_exists('upload/' .$file_name))
{
echo'The file <strong>"'.$_FILES['userfile']['name'].'"</strong>already exist to our server<br>You have to rename the file in your pc!';
} 

NOTE:
Replacing empty spaces with " _  " . can be necessary when you linking to a uploaded file. The empty spaces can generate  big problems ...

you can use also  "-"