php突破上传验证后缀

$allowedExtensions = ['jpg', 'jpeg', 'png', 'gif'];
$fileExtension = strtolower(pathinfo($_FILES['file']['name'], PATHINFO_EXTENSION));

if (!in_array($fileExtension, $allowedExtensions)) {
    die("Invalid file extension.");
}

function isImage($file) {
    $image = getimagesize($file);
    if ($image !== false) {
        return true;
    }
    return false;
}

if (!isImage($_FILES['file']['tmp_name'])) {
    die("Invalid image file.");
}

$fileName = uniqid() . '.' . $fileExtension;
move_uploaded_file($_FILES['file']['tmp_name'], 'uploads/' . $fileName);