php random image file name

Question

Okay im using a snippet I found on google to take a users uploaded image and put it in my directory under Content

But Im worried about duplicates so I was going have it upload the image as a Random number

well here is my code you can probably understand what im going for through it anyways

<label for="file">Profile Pic:</label> <input type="file" name="ProfilePic" id="ProfilePic" /><br />

<input type="submit" name="submit" value="Submit" />

$ProfilePicName = $_FILES["ProfilePic"]["name"];
$ProfilePicType = $_FILES["ProfilePic"]["type"];
$ProfilePicSize = $_FILES["ProfilePic"]["size"];
$ProfilePicTemp = $_FILES["ProfilePic"]["tmp_name"];
$ProfilePicError = $_FILES["ProfilePic"]["error"];

$RandomAccountNumber = mt_rand(1, 99999);  
echo $RandomAccountNumber; 
move_uploaded_file($ProfilePicTemp, "Content/".$RandomAccountNumber.$ProfilePicType);

And then basicly after all this Im going try to get it to put that random number in my database

Someone gave me a new snippet that looks like it will do what I want but now the file isnt making it all the way to my directory

$RandomAccountNumber = uniqid();
echo $RandomAccountNumber;

move_uploaded_file($ProfilePicName,"Content/".$RandomAccountNumber);

Answer 1

try using the php uniqid method to generate the unique id you need

http://php.net/manual/en/function.uniqid.php

$RandomAccountNumber = uniqid();
move_uploaded_file($ProfilePicTemp, "Content/" . $RandomAccountNumber);

Answer 2

When I upload images, I usually save it as the sha1() of the image's contents (sha1_file()). That way, you get two birds with one stone: You'll never (if you do, go fill out the closest lottery) get duplicate file names, AND, you'll prevent duplicate images (because duplicate images would have the same checksum).

Then, you have a database to sort out which image is which, and correctly display them to the user.

Answer 3

This is what I use when uploading pictures: a combination of session_id(), time() and a random string:

$rand = genRandomString();
$final_filename = $rand."_".session_id()."_".time();

function genRandomString() 
{
    $length = 5;
    $characters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWZYZ";

    $real_string_length = strlen($characters) ;     
    $string="id";

    for ($p = 0; $p < $length; $p++) 
    {
        $string .= $characters[mt_rand(0, $real_string_length-1)];
    }

    return strtolower($string);
}

I hope this help.

Answer 4

random != unique

No matter what method you use to generate a 'random' file name you're probably going to want to do this to avoid collisions.

$path = '/path/to/directory/';
do {
    $filename = some_function();
} while( file_exists($path.$filename) );

It's not super-necessary, but if you're just looking for peace of mind in case of a one-in-a-million filename collision then those couple extra lines will do the trick.

Answer 5

One of my favorite Coding Horror articles addresses why this approach is dumber than it looks, and you should use something like uniqid instead of mt_rand(1, 99999);...