PHP upload (w3schools script) with custom name

Question

im using a pre made php upload script from w3schools, but i dont know how i can modify the code to upload the file with a unique id instead of the original file name.

upload.php

<?php
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["fileToUpload"]["name"]);
$uploadOk = 1;
$imageFileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION));
// Check if image file is a actual image or fake image
if(isset($_POST["submit"])) {
    $check = getimagesize($_FILES["fileToUpload"]["tmp_name"]);
    if($check !== false) {
        echo "File is an image - " . $check["mime"] . ".";
        $uploadOk = 1;
    } else {
        echo "File is not an image.";
        $uploadOk = 0;
    }
}
// Check if file already exists
if (file_exists($target_file)) {
    echo "Sorry, file already exists.";
    $uploadOk = 0;
}
// Check file size
if ($_FILES["fileToUpload"]["size"] > 500000) {
    echo "Sorry, your file is too large.";
    $uploadOk = 0;
}
// Allow certain file formats
if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg"
&& $imageFileType != "gif" ) {
    echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed.";
    $uploadOk = 0;
}
// Check if $uploadOk is set to 0 by an error
if ($uploadOk == 0) {
    echo "Sorry, your file was not uploaded.";
// if everything is ok, try to upload file
} else {
    if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) {
        echo "The file ". basename( $_FILES["fileToUpload"]["name"]). " has been uploaded.";
    } else {
        echo "Sorry, there was an error uploading your file.";
    }
}
?>

Answer 1

Here's an example, it also provides you a flexibility on how many characters to use for filename.

function generateRandomString($length = 10) {
  return substr(str_shuffle(str_repeat($x='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ', 
                ceil($length/strlen($x)) )),1,$length);
}

$org_filename=basename($_FILES["fileToUpload"]["name"]);   
$ext = pathinfo($org_filename, PATHINFO_EXTENSION);

$target_file = $target_dir . generateRandomString(20) . '.' . $ext ;

Answer 2

For generating unique id, you can use php md5() and date() function. You can pass current date time in it so it will encrypt it and will generate a unique string.

Refer this - $target_file = $target_dir .md5(date('dmy h:i:s')). $ext; $target_file = $target_dir .md5(date('dmy h:i:s')). $ext;