Is relying on the MIME type for image validation a secure practice in PHP?

Relying solely on the MIME type for image validation in PHP is not a secure practice, as MIME types can be easily spoofed. To ensure secure image validation, it is recommended to use a combination of MIME type checking and additional image validation techniques, such as checking the image dimensions or using image processing libraries.

// Example of secure image validation in PHP
function validateImage($file) {
    $allowedMimeTypes = ['image/jpeg', 'image/png', 'image/gif'];
    $maxFileSize = 1048576; // 1MB

    if ($file['size'] > $maxFileSize) {
        return false;
    }

    $finfo = finfo_open(FILEINFO_MIME_TYPE);
    $mime = finfo_file($finfo, $file['tmp_name']);
    finfo_close($finfo);

    if (!in_array($mime, $allowedMimeTypes)) {
        return false;
    }

    // Additional validation steps like checking image dimensions can be added here

    return true;
}

// Example usage
if (isset($_FILES['image'])) {
    if (validateImage($_FILES['image'])) {
        // Image is valid, process it further
    } else {
        // Invalid image
    }
}