Giving uploaded images a unique name for mysqli

Question

I want to allow users to upload images without conflicting problems that may be caused by multiple users uploading images that potentially have the same image name. I am stumped on how to execute this and I have no idea where to start..

Here is my code:

 if(isset($_POST['submitimage'])){
                move_uploaded_file($_FILES['file']['tmp_name'],"pictures/".$_FILES['file']['name']);
                $con = mysqli_connect("localhost","root","","database");
                $q = mysqli_query($con,"UPDATE users SET image = '".$_FILES['file']['name']."' WHERE user_id = '".$_SESSION['user']."'");
                 header("Location: index.php");
        }
?>

Any help would be amazing. Thank you!

Answer 1

My solution is to generate a random string for each uploaded file, i.e.:

<?php
   if(!empty($_POST['submitimage'])){
                //get file extension.
                $ext = pathinfo($_FILES['file']['name'])['extension'];
                //generate the new random string for filename and append extension.
                $nFn = generateRandomString().".$ext";
                move_uploaded_file($_FILES['file']['tmp_name'],"pictures/".$nFn);
                $con = mysqli_connect("localhost","root","","database");
                $q = mysqli_query($con,"UPDATE users SET image = '{$nFn}' WHERE user_id = '{$_SESSION['user']}'");
                 header("Location: index.php");
        }

function generateRandomString($length = 10) {
    return substr(str_shuffle("abcdefghijklmnopqrstuvwxyz"), 0, $length);
}

?>