MySQL Slugify function

DROP FUNCTION IF EXISTS `slugify`;
DELIMITER ;;
CREATE DEFINER=`gaincity`@`localhost`
FUNCTION `slugify`(dirty_string varchar(200))
RETURNS varchar(200) CHARSET latin1
DETERMINISTIC
BEGIN
    DECLARE x, y , z Int;
    Declare temp_string, new_string VarChar(200);
    Declare is_allowed Bool;
    Declare c, check_char VarChar(1);

    set temp_string = LOWER(dirty_string);

    Set temp_string = replace(temp_string, '&', ' and ');

    Select temp_string Regexp('[^a-z0-9\-]+') into x;
    If x = 1 then
        set z = 1;
        While z <= Char_length(temp_string) Do
            Set c = Substring(temp_string, z, 1);
            Set is_allowed = False;
            If !((ascii(c) = 45) or (ascii(c) >= 48 and ascii(c) <= 57) or (ascii(c) >= 97 and ascii(c) <= 122)) Then
                Set temp_string = Replace(temp_string, c, '-');
            End If;
            set z = z + 1;
        End While;
    End If;

    Select temp_string Regexp("^-|-$|'") into x;
    If x = 1 Then
        Set temp_string = Replace(temp_string, "'", '');
        Set z = Char_length(temp_string);
        Set y = Char_length(temp_string);
        Dash_check: While z > 1 Do
            If Strcmp(SubString(temp_string, -1, 1), '-') = 0 Then
                Set temp_string = Substring(temp_string,1, y-1);
                Set y = y - 1;
            Else
                Leave Dash_check;
            End If;
            Set z = z - 1;
        End While;
    End If;

    Repeat
        Select temp_string Regexp("--") into x;
        If x = 1 Then
            Set temp_string = Replace(temp_string, "--", "-");
        End If;
    Until x <> 1 End Repeat;

    If LOCATE('-', temp_string) = 1 Then
        Set temp_string = SUBSTRING(temp_string, 2);
    End If;

    Return temp_string;
END;;
DELIMITER ;