How do i get the file extension of a file uploaded with php?

Question

This code works fine besides one problem after it generates a random string for the filename it doesn't keep the file extension.

<?php   
define("UPLOAD_DIR", "uploads/");

// process file upload
$file = $_FILES["file"];
if ($file["error"] !== UPLOAD_ERR_OK) {
    echo "<p>An error occurred.</p>";
    exit;
}

// verify the file type

$fileType = exif_imagetype($_FILES["file"]["tmp_name"]);
$allowed = array(IMAGETYPE_GIF, IMAGETYPE_JPEG, IMAGETYPE_PNG);
if (!in_array($fileType, $allowed)) {
    echo "<p>File type is not permitted.</p>";
    exit;
}

// ensure a random filename
$name = generateName();
$redirect = "http://rmaltsaar.net/rfile/uploads/" . $name;

// preserve file from temporary directory
$success = move_uploaded_file($file["tmp_name"], UPLOAD_DIR . $name);
if (!$success) {
    echo "<p>Unable to save file.</p>";
    exit;
}  else {
    echo "<p>Your file (" . $name . ") has been uploaded successfully!</p>";
    echo "<p>Redirecting to file</p>";
}

// This returns a random string for the filename

function generateName($max = 6) {
    $i = 0;
    $possible_keys = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $keys_length = strlen($possible_keys);
    $str = "";
    while($i < $max) {
        $rand = mt_rand(1, $keys_length-1);
        $str .= $possible_keys[$rand];
        $i++;
    }
    return $str;
}
?>

<meta http-equiv="refresh" content="8;url=<?php echo $redirect ?>">

So what i'm trying to figure out is how can i make the function generatename not just return a random string for the file but also return the files extension. like this:

return $str . $ext;

Answer 1

$filename = $_FILES['file']['name'];
$ext = pathinfo($filename, PATHINFO_EXTENSION);

$name = generateName().".$ext";