How can PHP developers ensure the security of file uploads on their websites?

PHP developers can ensure the security of file uploads on their websites by implementing proper validation, sanitization, and file type checking. They should also store uploaded files outside the web root directory to prevent direct access. Additionally, developers should consider limiting the file size and implementing measures such as renaming files to prevent malicious scripts from being executed. 

// Example PHP code snippet for securing file uploads
$uploadDir = 'uploads/';
$allowedTypes = ['jpg', 'jpeg', 'png', 'gif'];
$maxFileSize = 5 * 1024 * 1024; // 5MB

if ($_FILES['file']['error'] === UPLOAD_ERR_OK) {
    $fileName = $_FILES['file']['name'];
    $fileTmp = $_FILES['file']['tmp_name'];
    $fileSize = $_FILES['file']['size'];
    $fileType = strtolower(pathinfo($fileName, PATHINFO_EXTENSION));

    if ($fileSize > $maxFileSize) {
        die('File is too large.');
    }

    if (!in_array($fileType, $allowedTypes)) {
        die('Invalid file type.');
    }

    $newFileName = uniqid('', true) . '.' . $fileType;
    $uploadPath = $uploadDir . $newFileName;

    if (move_uploaded_file($fileTmp, $uploadPath)) {
        echo 'File uploaded successfully.';
    } else {
        echo 'Error uploading file.';
    }
} else {
    echo 'Error uploading file.';
}

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