expanding inside quotes problem

I've a problem with the folowing line $results = mysql_query("SELECT * FROM group WHERE postcode REGEXP '^$query[:digit:]+.*'", $db) when run I get: "Parse error: parse error, expecting T_STRING' or T_VARIABLE' or `T_NUM_STRING' " I think the problem is that php is treating the square brackets as a regular expression, and attempting to expand it(?). I can stop this by using single quotes, but then the variable in the string will not be expanded. I'm not sure what to escape in order that the query get passed correctly. I hope I've made it relatively clear. Thanks -- Andrew