Well you could do something like this:
function queryDB($db,$user_query)
{
$user_query = explode("+",str_replace(' ','',$user_query));
//Should now have:
//$user_query[0]=+computer
//$user_query[1]=+"apple imac"
$result = mysql_query("SELECT * FROM table WHERE column LIKE $user_query[0] AND column LIKE $user_query[1]",$db);
}
This may not be perfect but seems to work for what you asked.