What are some best practices for handling file uploads in PHP to ensure security and prevent vulnerabilities?

When handling file uploads in PHP, it is crucial to validate and sanitize user input to prevent security vulnerabilities such as file injection attacks. One best practice is to restrict the allowed file types and sizes to mitigate the risk of malicious uploads. Additionally, it is recommended to store uploaded files outside of the web root directory to prevent direct access by users. 

// Example of handling file uploads in PHP with security measures

// Define allowed file types and maximum file size
$allowedTypes = ['image/jpeg', 'image/png'];
$maxFileSize = 2 * 1024 * 1024; // 2MB

// Validate file type and size before uploading
if (in_array($_FILES['file']['type'], $allowedTypes) && $_FILES['file']['size'] <= $maxFileSize) {
    // Move uploaded file to a secure directory outside of the web root
    $uploadDir = '/path/to/secure/directory/';
    $uploadFile = $uploadDir . basename($_FILES['file']['name']);
    
    if (move_uploaded_file($_FILES['file']['tmp_name'], $uploadFile)) {
        echo 'File uploaded successfully.';
    } else {
        echo 'Failed to upload file.';
    }
} else {
    echo 'Invalid file type or size.';
}

Keywords

file uploads PHP security vulnerabilities prevention

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