public function toExtension($mime_type)
    {
        $mime_type = strtolower($mime_type);

        return array_search($mime_type, $this->dict) ?: null;
    }
public function toExtension($mime_type)
    {
        $mime_type = strtolower($mime_type);

        return array_search($mime_type, $this->dict) ?: null;
    }
public function toExtension ( $ mime_type ) { $ mime_type = strtolower ( $ mime_type ) ; return array_search ( $ mime_type , $ this -> dict ) ? : null ; }
Convert a mime type to the proper file extension.

@param string $mime_type
@return string|null
Convert a mime type to the proper file extension .