I'm trying to insert a variable into mysql table, but it does not do what i want (no error, it simply does not work)

```
$string = 'this is an example';
mysql_query("insert into tablename (columnname) values ????");

```

Anyone can help me how to insert `$string` into table tablename? I tried replacing `????` with `($string)`, `(".$string.")`, `$string`, but all of them does not insert the `$string` variable into the database.

Thanks in advance!