Are there any security risks associated with allowing users to upload multiple files in PHP?

Allowing users to upload multiple files in PHP can pose security risks such as file upload vulnerabilities, potential malicious file uploads, and possible denial of service attacks. To mitigate these risks, it is important to validate file types, limit file sizes, and store uploaded files in a secure directory outside of the web root. 

// Set upload directory outside of web root
$uploadDir = '/var/www/uploads/';

// Validate file types and limit file sizes
$allowedTypes = ['jpg', 'jpeg', 'png', 'gif'];
$maxFileSize = 5 * 1024 * 1024; // 5MB

foreach ($_FILES['files']['tmp_name'] as $key => $tmpName) {
    $fileName = $_FILES['files']['name'][$key];
    $fileSize = $_FILES['files']['size'][$key];
    $fileType = strtolower(pathinfo($fileName, PATHINFO_EXTENSION));

    if (!in_array($fileType, $allowedTypes) || $fileSize > $maxFileSize) {
        // Handle invalid file type or size
    } else {
        move_uploaded_file($tmpName, $uploadDir . $fileName);
    }
}

Keywords

file upload security risks PHP file validation file handling

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