php 没有文件被上传

<form action="upload.php" method="post" enctype="multipart/form-data">
    <input type="file" name="file">
    <input type="submit" value="Upload">
</form>

upload_max_filesize = 2M
post_max_size = 8M

chmod 755 /path/to/upload/directory

<?php
if ($_SERVER['REQUEST_METHOD'] == 'POST' && isset($_FILES['file'])) {
    $file = $_FILES['file'];
    $uploadPath = '/path/to/upload/directory/' . basename($file['name']);

    if ($file['error'] === UPLOAD_ERR_OK) {
        if (move_uploaded_file($file['tmp_name'], $uploadPath)) {
            echo 'File is valid, and was successfully uploaded.';
        } else {
            echo 'Upload failed.';
        }
    } else {
        echo 'Error uploading file.';
    }
} else {
    echo 'No file uploaded.';
}
?>