YA: Simple File Upload WC

<?php
// Lets make this easier to read/edit
// I also broke up the 'br' tags, as Yahoo doesn't like them
$f = $_FILES['file'];
$acceptedTypes = Array('image/gif','image/jpeg','image/png','image/jpg');
$fileSizeLimit = 20; // In Kb
$fileSizeLimit *= 1024; // Change File Size Limit to bytes

// As oppose to writting $_FILES['file'] each time, now we just write ($f);
// in_array($needle, $haystack) return true if the $needle is in the $haystack, false otherwise

// For Debugging Purposes, here is a function to explain the Upload Error Codes.
function uploadErrorMsg($e){
    $errors = array(
        0 => 'There was not error',
        1 => 'The uploaded file exceeds the Server\'s Maximum Allowable File Size',
        2 => 'The uploaded file exceeds the Form\'s Maximum Allowable File Size.',
        3 => 'The uploaded file was only partially uploaded, then interrupted or the connection was dropped.',
        4 => 'No file was uploaded.',
        6 => 'Missing a temporary folder. The server requires a temporary folder for file uploads.', // Internal Operations Error
        7 => 'Failed to write file to disk.', // Internal Server Error
        8 => 'A PHP extension stopped the file upload.' // PHP Extension Library stopped the upload.
    );
    return $errors[$e];
}



if ( in_array($f['type'], $acceptedTypes) && $f["size"] < $fileSizeLimit){
    if ($f["error"] > 0){
        echo "Return Code: " . $f["error"] . "<b" . "r>";
        echo uploadErrorMsg($f['error']) . "<b" . "r>";
    } else {
        echo "Upload: " . $f["name"] . "<b" . "r>";
        echo "Type: " . $f["type"] . "<b" . "r>";
        echo "Size: " . ($f["size"] / 1024) . " Kb<b" . "r>";
        echo "Temp file: " . $f["tmp_name"] . "<b" . "r>";

        if (file_exists("upload/" . $f["name"])){
            echo $f["name"] . " already exists. ";
        } else {
            move_uploaded_file($f["tmp_name"], "upload/" . $f["name"]);
            echo "Stored in: " . "upload/" . $f["name"];
        }
    }
} else {
    echo "Invalid file";
}
?>