secure query string before sending it to mysql

Hi,

I'm working on a database class of my own. I've got the following method:

/**
* query() performs a query on the selected database
*/
function query($dbQuery)
{
if (is_string($dbQuery))
$this->dbQuery = $dbQuery;
else
die("The submitted query isn't a string");

$this->queryResult = mysql_query($this->dbQuery)
or die("Couldn't perform the query: " . mysql_error());
}

In the best of all words, variables that are part of the query string has
been validated before going into the query. But if I sometimes forget to
verify that user input doesn't contain dangerous code, I want to add some
validating mechanism into the method above as well.

$dbQuery will be query string like "INSERT INTO $article_table SET
a_header = '$a_header'". Is there anything I can do, inside the method, to
increase security?

--
anders thoresson