A class that guesses the file extension either from raw binary or base64 data

FileExtensionGuesserService.php

<?php

namespace Acme\AcmeBundle\Service;

class FileExtensionGuesserService
{
    /**
     * Guesses the mime type of a file by raw binary or base64 encoded content
     * and returns its file type.
     * 
     * @param binary | string $rawData
     * @return string | null
     */
    public function guessFromRaw($rawData)
    {
        // checks is raw data is base64 encoded and decodes to be raw binary
        $isBase64 = \base64_encode(\base64_decode($rawData, true) === $rawData);
        
        if ($isBase64) {
            $rawData = \base64_decode($rawData);
        }
        
        // guess the mime type
        $finfo = new \finfo(FILEINFO_MIME_TYPE);
        $mimeType = $finfo->buffer($rawData);

        return $this->getExtensionFromMimeType($mimeType);
    }

    /**
     * Returns the extension by mime type name.
     * 
     * @param string $mimeType
     * @return string | null
     */
    private function getExtensionFromMimeType($mimeType)
    {
        $mimeTypesExtensionsMap = array(
            "image/jpeg" => "jpg",
            "image/pjpeg" => "jpg",
            "image/png" => "png",
            "image/x-png" => "png",
            "image/gif" => "gif",
            "image/svg+xml" => "svg",
            "application/xml" => "svg",
            "text/xml" => "svg",
            "image/bmp" => "bmp",
            "image/x-bmp" => "bmp",
            "image/x-bitmap" => "bmp",
            "image/x-xbitmap" => "bmp",
            "image/x-win-bitmap" => "bmp",
            "image/x-windows-bmp" => "bmp",
            "image/ms-bmp" => "bmp",
            "image/x-ms-bmp" => "bmp",
            "application/bmp" => "bmp",
            "application/x-bmp" => "bmp",
            "application/x-win-bitmap" => "bmp"
        );
        
        if (isset($mimeTypesExtensionsMap, $mimeType)) {
            return $mimeTypesExtensionsMap[$mimeType];
        } else {
            return null;
        }
    }
}