Multiple queries in one statement

I maintain a database of member names for our organization, and use php to maintain that database for such things as adding a member, updating a member, and deleting a member.

The problem is with delete member. For example, if I have two members with the last name of Smith, my query results page displays both of them, with a delete option for each. However, if I click the delete button for John Smith, Mike Smith is also deleted.

How do I set my query so that only the selected member is deleted? The current query for that is:
$query="DELETE FROM members WHERE lastname='$lastname'";

As u said u have two members with Smith as lastname but first name differs,
So u can write the query like
Query=DELETE FROM members WHERE firstname LIKE 'John%' (John Smith)
or 'Mike%'(Mike Smith);
or else u can use '=' operator instead of LIKE operator in ur query.
Hope it will be useful.

If u want to delete the records only using lastname.....the following reply won't work.If not it will.......
As u said u have two members with Smith as lastname but first name differs,
So u can write the query like
Query=DELETE FROM members WHERE firstname LIKE 'John%' (John Smith)
or 'Mike%'(Mike Smith);
or else u can use '=' operator instead of LIKE operator in ur query.
Hope it will be useful.