llHTTPRequest, php/mysql and security

So I'm working on building llHTTPRequest into one of my scripts and storing some information on a remote database via php/mysql. Let's say that my php script wants to use $headers["X-SecondLife-Object-Key"] and $headers["X-SecondLife-Object-Name"] in a mysql query. How can I check these strings in the php script to make sure no one hijacks the query to mess with my database? Are there particular characters to check for? Can I check a string to make sure it only includes alpha-numeric characters (and dashes for keys)?

in PHP: mysql_real_escape_string()