public static function is_extension_invalid($extension, $oldextension = '') {
        $extension = trim($extension);
        if ($extension === '' || $extension[0] === '.') {
            return true;
        }

        $mimeinfo = get_mimetypes_array();
        if ($oldextension !== '') {
            unset($mimeinfo[$oldextension]);
        }

        return array_key_exists($extension, $mimeinfo);
    }
public static function is_extension_invalid($extension, $oldextension = '') {
        $extension = trim($extension);
        if ($extension === '' || $extension[0] === '.') {
            return true;
        }

        $mimeinfo = get_mimetypes_array();
        if ($oldextension !== '') {
            unset($mimeinfo[$oldextension]);
        }

        return array_key_exists($extension, $mimeinfo);
    }
public static function is_extension_invalid ( $ extension , $ oldextension = '' ) { $ extension = trim ( $ extension ) ; if ( $ extension === '' || $ extension [ 0 ] === '.' ) { return true ; } $ mimeinfo = get_mimetypes_array ( ) ; if ( $ oldextension !== '' ) { unset ( $ mimeinfo [ $ oldextension ] ) ; } return array_key_exists ( $ extension , $ mimeinfo ) ; }
Checks if the given file type extension is invalid.
The added file type extension must be unique and must not begin with a dot.

@param string $extension Extension of the file type to add
@param string $oldextension Extension prior to update (empty string if adding new type)
@return bool True if it the file type trying to add already exists
Checks if the given file type extension is invalid . The added file type extension must be unique and must not begin with a dot .